فهرست مطالب

  • سال سی و چهارم شماره 3 (مرداد و شهریور 1399)
  • تاریخ انتشار: 1399/06/31
  • تعداد عناوین: 16
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  • محمدحسن نادری، مهدی ذاکری نیا*، میثم سالاری جزی صفحات 515-532

    در مطالعات برنامه ریزی توسعه پایدار منابع آب در حوضه های آبخیز، درک، توصیف و طراحی رژیم جریان، نقش مهمی در برقراری تعادل فرآیندهای هیدرولوژیکی و اکولوژیکی و تداوم حیات اکوسیستم های رودخانه ای دارد. جریان اکولوژیکی پایه و اساس حفاظت از زیستگاه ماهیان رودخانه ای و از ارکان مدیریت اکوسیستم رودخانه است که بایستی به رسمیت شناخته شود، اما بدان اهمیت خاصی داده نمی شود. پایش جریان زیست محیطی در طول رودخانه ، برای اطمینان از انتقال و توزیع جریان مطلوب اکولوژیکی مورد نیاز به اکوسیستم های آبی پایین دست، ضروری است. از این رو در پژوهش حاضر به منظور ایجاد شرایط پایدار اکولوژیک در رودخانه زرین گل استان گلستان، طی محاسبات گام به گام تحلیل اکوهیدرولیکی زیستگاه گونه سیاه ماهی Capoeta gracilis (Keyserling, 1861) و تحلیل جریان اکولوژیکی با استفاده از روش های هیدرولوژیکی تنانت و انتقال منحنی تداوم جریان و مدل شبیه سازی زیستگاه، مورد بررسی قرار گرفت. نتایج نشان داد با انجام شبیه سازی هیدرولیکی و آنالیز سری زمانی دبی- فیزیک زیستگاه با استفاده از منحنی های شاخص مطلوبیت، محدوده رژیم جریان موردنیاز برای تامین پتانسیل اکولوژیکی زیستگاه گونه شاخص، بین 49/2 و 58/0 مترمکعب برثانیه به ترتیب در ماه های فروردین و آبان، با میانگین دبی سالانه 25/1 مترمکعب برثانیه (معادل 59 درصد جریان طبیعی رودخانه) می باشد. همچنین مقایسه میزان تخصیص آب برای تامین جریان زیست محیطی با روش تنانت در رودخانه مورد مطالعه نشان داد، کمبود جریان در فصول تابستان و زمستان (جریان رودخانه کمتر از جریان زیست محیطی است) مشاهده می شود. در نهایت این نتیجه به عمل آمد که روش های دیگر تامین جریان زیست محیطی (انتقال منحنی تداوم جریان و شبیه سازی زیستگاه)، مقادیر بالاتر از 30 درصد میانگین جریان سالانه را فراهم می کند، که محافظت بهتر جریان را برای زیستگاه رودخانه فراهم می کنند. بر اساس نتایج این مطالعه، توزیع مطلوبیت زیستگاهی در طول رودخانه زرین گل، تحت تاثیر پارامترهای هندسی، هیدرولیکی و میزان دبی جریان، بیانگر شرایط مطلوب زیستگاهی گونه سیاه ماهی در محدوده پایین دست و شرایط ضعیف در محدوده بالادست رودخانه می باشد. در نهایت، رویکرد مدل اکوهیدرولیکی شبیه سازی زیستگاه، نسبت به روش های هیدرولوژیکی بسیار انعطاف پذیرتر بوده و می تواند برای تجزیه و تحلیل های میزان مطلوبیت زیستگاه ماهیان در مدیریت اکوسیستم رودخانه، مورد استفاده قرار گیرد.

    کلیدواژگان: جریان زیست محیطی، رودخانه زرین گل، سیاه ماهی، مساحت قابل استفاده وزنی، مطلوبیت زیستگاه
  • عبدالرحیم فیروزی، سید مجید میرلطیفی*، حامد ابراهیمیان طالشی صفحات 533-547

    امروزه فعالیت های انسانی در بخش کشاورزی به خصوص در نواحی خشک و نیمه خشک برروی چرخه و انتقال آب سطحی و زیرزمینی تاثیر به سزایی داشته است. از این رو، بررسی وضعیت منابع آب زیرزمینی دارای اهمیت است. تخمین های مناسب و قابل اعتماد تغذیه ناشی از آبیاری بر آب زیرزمینی می تواند در این امر موثر باشد. به منظور بررسی تاثیر آبیاری بر تغذیه آبخوان، یک مزرعه گندم، دو مزرعه جو و سه مزرعه چغندرقند در شهرستان میاندوآب و دو مزرعه گندم در شهرستان مهاباد در حوضه دریاچه ارومیه تحت مدیریت کشاورزان انتخاب شدند. شبیه سازی نفوذ با استفاده از مدل HYDRUS-1D در طول دوره رشد محصولات مذکور انجام شد. با پایش رطوبت خاک در این مزارع، مدل با رطوبت های خاک اندازه گیری شده از طریق حل معکوس، واسنجی و صحت سنجی شد. دقت مدل بعد از انجام مراحل واسنجی و صحت سنجی در تخمین جریان آب در داخل خاک مناسب بود. مقادیر ضریب تعیین و خطای جذر میانگین در مرحله واسنجی به ترتیب بین 6/0 تا 85/0 و 17/0 تا 033/0  به دست آمد. ضریب تعیین و خطای جذر میانگین مربعات در مرحله صحت سنجی نیز به ترتیب بین 62/0 تا 88/0 و 002/0 تا 023/0 () به دست آمد. پس از واسنجی مدل، تغییرات رطوبت در اعماق مختلف خاک تا سطح آبخوان توسط مدل شبیه سازی شد. پیشروی رطوبت در عمق خاک از عمق 7/0 تا 7/4 توسط مدل برآورد شد. آب آبیاری سبب تغذیه آب زیرزمینی در مزارع مورد مطالعه شد که این میزان تغذیه در اثر آبیاری و بارندگی، بسته به نوع خاک، نوع کشت و مدیریت آبیاری در مزارع مختلف متفاوت بود. بیشترین تغذیه در مزرعه H3 با خاک لوم رسی شنی به مقدار 221 میلی متر از 789 میلی متر مجموع آبیاری و بارندگی (28 درصد) در طول فصل کشت گیاه جو بدست آمد.

    کلیدواژگان: آبیاری، تغذیه، سطح آبخوان، شبیه سازی، HYDRUS
  • نادر کوهی چله کران، حسین دهقانی سانیج*، امین علیزاده، الهه کنعانی صفحات 549-563

    پژوهش حاضر با هدف بررسی تاثیر رژیم های آبیاری قطره ای و سطوح مختلف کود نیتروژن بر عملکرد و اجزای عملکرد ذرت دانه ای (SC 704) و تغییرات رطوبت خاک در استان کرمان طی سال های زراعی 1393-1391 انجام گردید. طرح آزمایشی به صورت کرت های خرد شده در قالب بلوک های کامل تصادفی شامل سه تیمار اصلی رژیم های آبیاری (I1=100، I2=80 و I3= 60%ETc) و پنج تیمار فرعی سطح کود نیتروژنه N1 = 0)، N2= 50، N3= 100، N4= 150 و N5= 200 کیلوگرم بر هکتار) اجرا شد. نتایج نشان داد که بیشترین میزان عملکرد (85/8 تن در هکتار) به تیمار I1 اختصاص یافت. کاربرد نیتروژن بیش از اندازه تاثیر منفی در عملکرد دانه ذرت داشت. مصرف بیشترکود نیتروژن موجب طولانی شدن دوره رشد رویشی، افزایش شاخ و برگ گیاه و متعاقب آن موجب افزایش عملکرد بیولوژیک گیاه می شود و این امر می تواند موجب کاهش عملکرد دانه ذرت گردد. همچنین در خاک هایی که کمبود نیتروژن دارند با افزودن نیتروژن عملکرد دانه ذرت افزایش می یابد ولی پس از رسیدن به حداکثر عملکرد افزودن نیتروژن تاثیری نداشته و باعث کاهش عملکرد می شود. اثرات متقابل تیمار ها نشان داد که تیمارهای I1N4 بیشترین (6/10 تن در هکتار) و تیمار I3N1 کمترین (24/1 تن در هکتار) عملکرد دانه ذرت را داشتند. بیشترین و کمترین اجزای عملکرد ذرت به ترتیب در تیمارهای I1N4 و I3N5 مشاهده شد. بیشترین میزان کارایی مصرف آب (268/1 کیلوگرم بر متر مکعب) در تیمار I2N4 و کمترین آن (068/0 کیلوگرم بر متر مکعب) در تیمار I3N1 بدست آمد. رطوبت باقی مانده در خاک با کاهش مقدار آب آبیاری و کود نیتروژن در 20 روز پس از کشت کاهش یافت. در 45 روز بعد از کاشت و در عمق 10-0 سانتی متری، رطوبت باقی مانده در خاک برای تیمار های I1، I2 و I3 به کمتر از نقطه پژمردگی دایم رسیدند. نتایج حاصل از این پژوهش این مهم را به ما نشان می دهد که تحت شرایط تنش آبی، امکان دسترسی به میزان عملکرد و کارایی مصرف آب بیشتر محصول به همراه شرایط رطوبتی مساعد و مطلوب، با اعمال میزان مناسب سطوح کودی امکان پذیر است و و تیمار I2N4 می تواند گزینه کاربردی مناسبی باشد.

    کلیدواژگان: رژیم آبیاری، رطوبت خاک، سطوح مختلف کودی، قطره ای سطحی
  • بهجت سرچشمه*، جواد بهمنش، وحید رضاوردی نژاد صفحات 565-577

    آب نقشی مهم برای رفاه انسانها و محیط زیست دارد. مردم برای مصارف کشاورزی، صنعتی و خانگی از آب رودخانه استفاده می کنند. علاوه بر این، برآورده شدن نیاز زیست محیطی اکوسیستم رودخانه بسیار مهم خواهد بود. کمبود آب یک محدودیت اصلی و جدی برای توسعه اقتصادی-اجتماعی در کشورهای در حال توسعه و یک خطر برای معیشت مردم در نقاط مختلفی از جهان شده است. در سال های اخیر دریاچه ارومیه که در شمال غرب ایران واقع شده است با کمبود جدی آب مواجه شده است. زرینه رود یکی از مهم ترین رودخانه هایی است که آب دریاچه را تامین می کند. در این مطالعه براساس داده های ماهانه کمیت آب از سال 1365تا 1395 ایستگاه نظام آباد رودخانه زرینه رود، نیاز جریان زیست محیطی با روش تنانت محاسبه شد. همچنین داده های کیفی و کمی آب و نیاز جریان زیست محیطی برای ارزیابی کمبود آب به وسیله شاخص SQQE مورد بررسی قرار گرفت. نتایج نشان داد که متوسط نیاز جریان زیست محیطی برابر 106× 400 مترمکعب درسال و برابر با % 11/33 متوسط جریان سالانه جهت مدیریت اکولوژیکی و حفظ اکوسیستم رودخانه در سطح خوب می باشد. شاخص های کمی و کیفی به ترتیب 02/1 و 08/1 محاسبه شدند. محاسبات نشان می دهند، شاخص کمی، همان شاخص اسمختین، می باشد. این مقادیر نشان می دهند که هر دو شاخص کمی و کیفی بالای حد 1 هستند و در نتیجه این ایستگاه در حال تحمل کمبود آب مربوط به کمیت و کیفیت برای مقدار معین نیاز جریان زیست محیطی می باشد. بنابراین چاره اندیشی مدیریتی مناسب، ضروری به نظر می رسد.

  • صغری توفیق، داریوش رحیمی*، حجت الله یزدان پناه صفحات 579-592

    هدف از این مطالعه ارزیابی مدل CERES-WHEAT برای برآورد تبخیرتعرق، نیازآبی، عملکرد و کارایی مصرف آب محصول گندم در دشت شهرکرد است. تحقیقات مزرعه ای برای انتخاب مناسب ترین روش های کاشت یا برآورد محصول معمولا هزینه بر بوده و نیاز به زمان طولانی دارد. مدل های شبیه سازی رشد محصول مناسب ترین روش برای کم کردن این هزینه و زمان می باشند. مدل CERES-WHEAT یکی از کارآمدترین مدل ها برای شبیه سازی رشد گیاه گندم است. برای تعیین کارایی و انتخاب مدل بهینه برآورد تبخیرتعرق و عملکرد محصول گندم از داده های لایسیمتر ثبت شده ایستگاه تحقیقات کشاورزی استفاده شد. آنالیز حساسیت روش های برآورد تبخیرتعرق فایو پنمن مونتیث و پرستلی تیلور مدل CERES-WHEAT، مشخص کرد که روش فایو-پنمن-مانتیث با مقادیر  MADبرابر 95/0 ، MSEبرابر 95/0 ، RMSE برابر 57/1 و ضریب همبستگی 0/97 روش بهینه ای برای برآورد تبخیر تعرق محصول گندم در دشت شهرکرد است. نتایج آزمون آماری نشان داد که عملکرد محصول با این روش دارای حداقل خطا با داده های مشاهداتی بود. خروجی های مدل نشان داد روش فایو-پنمن-مونتیث مدل CERES-WHEAT کارایی بالایی برای شبیه سازی رشد و برآورد تبخیر تعرق گندم در شرایط آب و هوایی شهرکرد دارد.

    کلیدواژگان: پرستلی تیلور، تبخیرتعرق، فائو پنمن مونتیث، لایسیمتر، DSSAT-CERES-WHEAT
  • نرگس محراب*، مصطفی چرم، مجتبی نوروزی مصیر صفحات 593-608

    با توجه به پیامدهای آلودگی فلزات سنگین در محیط زیست، آلودگی زدایی این فلزات از اهمیت بالایی برخوردار است. در این تحقیق کارایی کلات کننده نیتریلوتری استیک اسید (NTA) بر آبشویی کادمیوم و جذب آن توسط گیاه ذرت در یک خاک آلوده در آزمایشی گلخانه ای بررسی گردید. در این مطالعه از سه سطح کادمیوم (0، 25 و 50 میلی گرم بر کیلوگرم خاک) و سه سطح کلات NTA (0، 15 و 30 میلی مول در لیتر در گلدان 8 کیلوگرمی) در خاکی با بافت لومی در کشت و عدم کشت گیاه ذرت و تحت شرایط سه دور آبیاری استفاده گردید. NTA طی سه مرحله بصورت محلول به گلدان ها اضافه گردید. نتایج نشان داد که با افزایش سطح آلودگی کادمیوم و مقدار NTA مصرفی، میزان کادمیوم زه آب و همچنین جذب کادمیوم توسط گیاه ذرت افزایش یافت. سطوح مختلف کادمیوم و NTA در دور اول آبشویی اختلاف معنی داری در کادمیوم شسته شده نشان دادند و در دو دور بعدی تفاوت قابل ملاحظه ای دیده نشد. میزان کادمیوم آبشویی شده از خاک گلدان های بدون کشت گیاه در تیمار 50 میلی گرم بر کیلوگرم کادمیوم با کاربرد 15 و 30 میلی مول NTA نسبت به عدم کاربرد NTA به ترتیب 8 و 4/15 برابر افزایش داشت. درصورتی که در تیمارهای مشابه در حضور گیاه ذرت، میزان آبشویی کادمیوم در خاک به ترتیب 8/5 و 6 برابر نسبت به عدم کاربرد NTA افزایش نشان داد. کادمیوم جذب شده توسط گیاه ذرت در تیمارهای حاوی 50 میلی گرم بر کیلوگرم کادمیوم در کاربرد 30 میلی مول NTA حداکثر بوده و این مقدار 57 درصد بیش از عدم کاربرد NTA اندازه گیری شد. NTA با کاهش در pH خاک و انحلال کربنات کلسیم از خاک بر افزایش کادمیوم آبشویی شده و کادمیوم جذب شده توسط گیاه اثر معنی داری نشان داد. این نتایج به خوبی اثر توام NTA و گیاه ذرت در پالایش کادمیوم از خاک آلوده را نشان می دهد.

    کلیدواژگان: آبشویی، کادمیوم خاک، گیاه پالایی، نیتریلوتری استیک اسید (NTA)
  • حسین باقری، حمید زارع ابیانه*، عزیزالله ایزدی صفحات 609-622

    هدف مطالعه حاضر بررسی اثر ورمی کمپوست بر ویژگی های شیمیایی، فیزیکی، هیدرولیکی و آبشویی املاح و کلوییدهای خاک است. به منظور اصلاح خاک، 45/1 درصد وزنی ورمی کمپوست با خاک طبیعی مخلوط و ویژگی های فیزیکی، شیمیایی و هیدرولیکی دو خاک طبیعی و خاک دارای ورمی کمپوست تعیین گردید. سپس، ستون هایی با طول و قطر 20 و 95/5 سانتی متر تهیه و با 10 سانتی متر خاک پر شد تا عمل آبشویی به مدت 24 ساعت در حالت اشباع به درون آن ها انجام شود. محلول های خروجی در زمان های مختلف جمع آوری و مقادیر سدیم، نیترات، کربن آلی محلول، کل املاح محلول (TDS) و کلویید پس از اندازه گیری به صورت تجمعی تا 6 و 24 ساعت آبشویی محاسبه و مقایسه میانگین ها در سطح 5% انجام شد. ورمی کمپوست، از ویژگی های شیمیایی ماده آلی، کربن آلی، نیترات قابل استخراج، سدیم محلول، سدیم محلول و تبادلی، EC و TDS را به اندازه 42/12، 9/12، 96/118، 43/80، 48/44، 4/109 و 4/109 درصد افزایش و pH را 35/2 درصد کاهش داد. کاهش 81/3 درصدی چگالی ظاهری، افزایش 38/1، 25/7 و 6/5 درصدی تخلخل، هدایت هیدرولیکی و سرعت آب حفره ای و جابجایی منحنی رطوبتی به سمت رطوبت های بیشتر در اطراف نقطه اشباع و پژمردگی دایم از دیگر اثرات ورمی کمپوست است. طبق نتایج آبشویی، ورمی کمپوست موجب آبشویی معنی دار سدیم، نیترات، کربن آلی، TDS و کلویید خاک در سطح احتمال 5 درصد و کاهش نرخ آن ها در زمان های طولانی تر شد. علی رغم نتایج مثبت کاربرد ورمی کمپوست، فرآیند آبشویی24 ساعته به سبب خروج تنها 8 درصد از TDS بخش ورمی کمپوست خاک، نقش موثری در کاهش شوری خاک نداشت در حالی که سبب خروج 6/44 درصد از نیترات ورمی کمپوست خاک شد که می تواند نگران کننده باشد. با توجه به اینکه این مطالعه تنها بر روی یک خاک شنی لومی در شرایط آزمایشگاهی انجام شده لذا نتایج آن قابل تعمیم به دیگر خاک ها نبوده و برای خاک های با بافت متفاوت انجام مجدد این مطالعات توصیه می گردد.

    کلیدواژگان: ضرایب هیدرولیکی خاک، منحنی رطوبتی خاک، آبشویی کربن آلی محلول، آبشویی نیترات، آبشویی کلوئید
  • الهام مهرابی گوهری، حمیدرضا متین فر*، روح الله تقی زاده مهرجردی، اعظم جعفری صفحات 623-635

    طیف سنجی مریی و مادون قرمز نزدیک (VIS-NIR) به طور گسترده ای برای تخمین خصوصیات فیزیکی خاک و اخیرا برآورد بافت خاک استفاده می شود. مطالعه حاضر با هدف پیش بینی احتمالی بافت خاک با استفاده از اندازه گیری های طیفی و مدل های شبکه عصبی مصنوعی و رگرسیون حداقل مربعات جزیی انجام گرفته است. بر اساس تکنیک هایپرکیوب، محل 115 پروفیل شناسایی و سپس نمونه برداری از افق های خاک انجام گرفت، درصد شن و رس و سیلت نمونه های خاک اندازه گیری شد. رگرسیون حداقل مربعات جزیی (PLSR) و شبکه عصبی مصنوعی (ANN) برای مدل سازی درصد رس، شن و سیلت خاک مقایسه شدند. نتایج این بررسی نشان داد که شبکه عصبی مصنوعی نسبت به رگرسیون حداقل مربعات جزیی کارایی بهتری داشت، برای هر دو مدل از محدوده خاصی از طول موج (بین 400 -2450 میکرون با اعمال پیش پردازش ها و حذفیات یکسان) استفاده گردید. هنگامی که مدل رگرسیون مربعات جزیی اجرا شد، دقت بسیار پایینی داشت (R2 ~0.1-0.3)، در مقابل، روش شبکه عصبی-مصنوعی مقدار R2 به ترتیب برای رس، شن و سیلت 70/0, 76/0و 73/0 بود و میانگین ریشه مربعات خطا به ترتیب 14/9، 54/5 و 01/7 گرم بر کیلوگرم براساس داده های آزمون (20 درصد) به دست آمد که نشان دهنده دقت بالاتر و خطای کمتر مدل شبکه عصبی-مصنوعی می باشد. از آنجایی که رابطه بین درصد ذرات خاک و بازتاب طیفی خاک خطی نیست، به نظر می رسد روش شبکه عصبی-مصنوعی برای بررسی و تجزیه و تحلیل رابطه بین اجزای بافت خاک و داده های طیفی مناسب باشد.

    کلیدواژگان: رگرسون حداقل مربعات جزئی، پیش بینی، مدل سازی، طیف سنجی مرئی مادون قرمز، شبکه عصبی مصنوعی
  • هدی حسینی*، مجید فکری، محمدهادی فرپور، مجید محمودآبادی صفحات 637-648

    آگاهی از تاثیر اجزای مختلف خاک همانند ماده آلی و کربنات ها بر قابلیت دسترسی فسفر در خاک جهت تغذیه گیاه و مدیریت حاصلخیزی خاک مهم است. در این مطالعه تاثیر حذف ماده آلی و کربنات ها بر رفتار جذب فسفر در شش نمونه خاک در سه تکرار و سه تیمار (تیمار هیپوکلریت سدیم، تیمار استات سدیم و خاک شاهد (بدون تیمار)) مورد مطالعه قرار گرفت. نتایج نشان داد که معادلات لانگمویر و فروندلیچ برازش خوبی بر داده های جذب فسفر نشان دادند. حذف ماده آلی باعث افزایش حداکثر جذب فسفر (qmax) با دامنه 37 تا 104 میلی گرم بر کیلوگرم نسبت به خاک های تیمار نشده شد. برعکس، با حذف کربنات ها از خاک ها، حداکثر جذب فسفر (qmax) در محدوده 43 تا 345 میلی گرم بر کیلو گرم نسبت به خاک های تیمار نشده کاهش نشان داد. ثابت انرژی پیوند (Kl) بعد از حذف مواد آلی و کربنات ها به ترتیب 03/17 درصد افزایش و 78/28 درصد کاهش یافت. نیاز استاندارد فسفر در خاک های مورد مطالعه بعد از حذف مواد آلی 43/14 درصد افزایش و حذف کربنات ها از خاک های مورد مطالعه نیاز آن ها را به فسفر 5/40 درصد کاهش داد. جهت مدیریت کارامد فسفر در خاک های کشاورزی توجه به میزان کربنات ها و کاهش آن در خاک اهمیت زیادی دارد و همچنین افزودن مواد آلی به خاک یا حداقل حفظ مواد آلی موجود در آن می تواند سبب افزایش کارایی مصرف فسفر در خاک شود.

    کلیدواژگان: جذب سطحی، فسفر، مواد آلی، نیاز استاندارد، هم دماها
  • رضا خدادادی، رضا قربانی نصر آبادی*، محسن علمائی، سید علیرضا موحدی نائینی صفحات 649-660

    از جمله روش های مناسب برای مقابله با شوری، تلقیح گیاهان زراعی با انواع مختلفی از باکتری های ریزوسفری محرک رشد گیاه می باشد. بدین منظور آزمایشی گلخانه ای در قالب طرح کاملا تصادفی با آرایش فاکتوریل در سه تکرار روی گیاه جو رقم کارون انجام شد. تیمارهای آزمایش شامل چهار سطح تلقیح باکتری (بدون تلقیح (شاهد)، ازتوباکتر، آزوسپریلوم و تلقیح تلفیقی ازتوباکتر و آزوسپیریلیوم) و دو سطح شوری (8 و 16 دسی زیمنس بر متر) بودند. نتایج نشان داد که تنش شوری تاثیر منفی ودر مقابل، تلقیح باکتری تاثیر مثبت و معنی داری بر ویژگی های رشدی گیاه داشت. کاربرد تلفیقی باکتری های ازتوباکتر و آزوسپیریلیوم بهینه ترین تیمار شناخته شد. تیمار تلفیقی سبب بهبود ویژگی های رشدی گیاه و افزایش محتوی کلروفیل در هر دو سطح شوری شد. بر این اساس، محتوی کلروفیل a، b و کل در سطح شوری بالا به ترتیب به میزان 49/86، 136/117 و 97/127درصد نسبت به شاهد افزایش یافت. همچنین تیمار تلفیقی به ترتیب افزایش 39/65 و 94/55 درصدی اسید آمینه پرولین را نسبت به شاهد در سطوح شوری 8 و 16 دسی زیمنس برمتر به همراه داشت. از سویی، تیمار تلفیقی در هر دو سطح شوری تاثیر معنی داری بر افزایش غلظت عناصر غذایی اندام هوایی داشت. بر این اساس در سطح شوری بالا به ترتیب افزایش 97/81، 80 و 67/66 درصدی غلظت نیتروژن، فسفر و پتاسیم در مقایسه با شاهد مشاهده شد. تجمع یون سدیم در تمامی تیمارهای باکتریایی در هر دو سطح شوری نسبت به تیمار شاهد کاهش یافت. این یافته ها نشان دهنده اثر مثبت تلقیح باکتریایی بر رشد و جذب عناصر غذایی جو تحت تنش شوری بود.

    کلیدواژگان: باکتری های محرک رشد، پرولین، شوری، کلروفیل
  • ساناز اشرفی سعیدلو، عباس صمدی، میرحسن رسولی صدقیانی*، محسن برین، ابراهیم سپهر صفحات 661-673

    افزایش سالانه ی قیمت کودهای شیمیایی پتاسیمی و نیز اثرات مخرب این کودها بر محیط زیست، اتخاذ راهکاری برای استفاده از پتاسیم بومی خاک را ضروری نموده است. استفاده از کودهای زیستی حاوی ریزجانداران سودمند از جمله این راهکارها محسوب می شود. این مطالعه با هدف مدل سازی و بررسی تاثیر نسبت های مختلف ورمی کمپوست، فلوگوپیت و گوگرد بر میزان انحلال و آزادسازی پتاسیم توسط باکتری Pseudomonas fluorescens و ارایه سطوح مطلوب این متغیرها برای تهیه کود زیستی کارآمد انجام گرفت. بر این اساس تعداد 20 آزمایش با استفاده از روش سطح پاسخ بر مبنای طرح مرکب مرکزی تعریف شد و اثر مقادیر مختلف متغیرهای ورمی کمپوست، کانی فلوگوپیت و گوگرد در چهار سطح کدبندی شده (+α،1+، 0، 1- و α-) بر میزان انحلال پتاسیم بررسی گردید. نتایج نشان دهنده ی کارآمدی بالای (8/0= RMSE و  949/0= R2) مدل طرح مرکب مرکزی در برآورد انحلال پتاسیم بود. بر اساس نتایج، برهم کنش ورمی کمپوست با گوگرد (0338/0>p) و برهم کنش فلوگوپیت با گوگرد (0083/0>p) نسبتا زیاد و معنی دار بود. نتایج تحلیل آماری ضرایب مدل طرح مرکب مرکزی حاکی از اثر مثبت و افزاینده ی ورمی کمپوست (X1) و اثر منفی و کاهنده فلوگوپیت (X2) و گوگرد (X3) بر افزایش انحلال پتاسیم بود. بطوری که با افزایش مقدار گوگرد از 25/10 به 75/39 درصد، انحلال پتاسیم تقریبا 61/31 درصد کاهش یافت. بر اساس پیش بینی شرایط بهینه برای انحلال پتاسیم، مقادیر 78/41 درصد ورمی کمپوست، 35/24 درصد فلوگوپیت و 25/10 درصد گوگرد منجر به بیشترین انحلال پتاسیم (27/109 میلی گرم بر لیتر) توسط باکتری سودوموناس فلورسنس می شود.

  • جعفر نیکبخت*، وحید عشقی، طاهر برزگر، علیرضا واعظی صفحات 675-688

    در پژوهش حاضر تاثیر کود اوره و آب مغناطیسی بر عملکرد و کارایی مصرف آب و کود در گیاه خیار بررسی شد. پژوهش به صورت آزمایش کرت های خرد شده در قالب طرح بلوک های کامل تصادفی با سه تکرار در مزرعه تحقیقاتی دانشگاه زنجان در سال 1397 انجام گرفت. تیمارهای آزمایش شامل سطوح کود نیتروژن از منبع اوره در 5 سطح (صفر، 25، 50، 75 و 100 درصد نیاز کودی اوره) و آب آبیاری (مغناطیسی و غیرمغناطیسی) بودند. آبیاری با سیستم قطره ای-نواری و کوددهی به صورت کودآبیاری تقسیطی انجام گرفت. نتایج نشان داد اثر سطوح کود اوره بر عملکرد میوه، کارایی مصرف آب و کود، تعداد میوه، سطح برگ و شاخص کلروفیل معنی دار بود. تیمار آب مغناطیسی بر کلیه صفات مورد ارزیابی بجز شاخص کلروفیل اثر معنی داری داشت. اثر متقابل تیمارهای آزمایش بر صفات کارایی مصرف آب و کود اوره و تعداد میوه معنی دار شد. بر اساس یافته ها، متوسط عملکرد، کارایی مصرف آب و کود اوره تیمار آب مغناطیسی به ترتیب 9/14، 13 و 5/110 درصد بیش تر از آب غیرمغناطیسی شد. نتایج نشان داد بهترین سطح کود اوره، 75 درصد نیاز کودی اوره بود که در شرایط استفاده از آب مغناطیسی نسبت به آب غیرمغناطیسی عملکرد، کارایی مصرف آب و کود را به ترتیب 4/18، 4/18 و 0/78 درصد افزایش داد.

    کلیدواژگان: آب مغناطیسی، خیار، کارایی مصرف آب، کارایی مصرف کود، کودآبیاری
  • امین موسوی، فرزین شهبازی*، شاهین اوستان، علی اصغر جعفرزاده، بودیمن میناسنی صفحات 689-705

    در این پژوهش، از دو مدل جنگل تصادفی و کیوبیست به عنوان یکی از پرکاربردترین تکنیک های نوین داده کاوی برای تهیه نقشه رقومی کربن آلی خاک در ساحل شرقی دریاچه ارومیه استفاده شد. بدین منظور با استفاده از روش نمونه برداری تصادفی مرتب شده در منطقه ای به وسعت 500 کیلومتر مربع تعداد 131 نمونه خاک سطحی (عمق 10-0 سانتی متری) و از دوسایت جداگانه برداشت شد. متغیرهای کمکی مورداستفاده در این تحقیق شامل شش باند مستقل برگرفته از تصویر OLI ماهواره لندست 8 (باندهای 2 تا 7)، تجزیه به مولفه های اصلی (PCA) باندها و همچنین تعداد 14 شاخص ترکیبی مربوط به تیرماه سال 1396می باشد. نتایج پیش بینی مدل در مرحله آزمون (25 درصد داده ها) نشان داد که مدل جنگل تصادفی با مقادیر (89/0 R2 =، 16/0RMSE = و 01/0ME =) صحت و کارایی بالاتری نسبت به مدل کیوبیست (85/0 R2 =، 21/0RMSE = و 03/0ME =) دارد. همچنین نتایج رتبه بندی اهمیت متغیرهای کمکی برای پیش بینی کربن آلی خاک نشان داد که پارامترهای شاخص مریی مقاومت اتمسفریک (VARI)، شاخص گیاهی نرمال شده (NDVI)، شاخص سنگی شده آهک دو (CRI2) و شاخص سنگی شده آهک یک (CRI1) دارای بیشترین تاثیر و شاخص گچ (GI) و برخی باند های مستقل از جمله باند 5 (B5) و باند 3 (B3) اهمیت کمتری نسبت به سایر شاخص ها دارند. به طور کلی نتایج نشان داد که مدل جنگل تصادفی در مقایسه با مدل کیوبیست به نحو مطلوبی قادر به مدل سازی و پیش بینی پراکنش مکانی کربن آلی خاک در منطقه مورد مطالعه بوده است.

    کلیدواژگان: جنگل تصادفی، کیوبیست، متغیرهای کمکی، مدل سازی، نقشه برداری رقومی
  • محمد مولائی آرپناهی، محمدحسن صالحی*، مصطفی کریمیان اقبال، زهره مصلح صفحات 707-720

    تغییر کاربری اراضی و شیوه های مدیریتی زمین علاوه بر تاثیر فراوانی که بر ویژگی های خاک دارد، می تواند منجر به از دست رفتن بسیاری از کاربردهای خاک گردد. بنابراین، مطالعات در زمینه اثر مدیریت های متفاوت روی ویژگی های مختلف خاک و در جهت مدیریت پایدار منابع خاک اهمیت فراوانی دارد. در این پژوهش اثر تغییر کاربری اراضی در کاربری های شامل جنگل بکر، باغ گردو، زمین کشاورزی و جنگل تخریب شده بر برخی از ویژگی های فیزیکی و شیمیایی کیفیت خاک در منطقه بازفت استان چهارمحال و بختیاری با شرایط یکسان از نظر تاثیر فرآیندهای خاک سازی مورد بررسی قرار گرفت. برای این منظور از هر کدام از چهار کاربری مورد نظر 10 نمونه خاک (در مجموع 40 نمونه) از عمق صفر تا 30 سانتی متری در قالب شبکه کاملا تصادفی جمع آوری و ویژگی های مورد نظر تجزیه شدند. با توجه به نتایج به دست آمده از این پژوهش  می توان بیان داشت که تغییر کاربری تاثیر معنی دار روی تمام ویژگی های مورد بررسی به غیر از درصد سیلت دارد. به طور کلی تخریب جنگل موجب کاهش شدید کیفیت خاک می گردد با این وجود تغییر کاربری از کشاورزی به باغ گردو منجر به بهبود کیفیت خاک می شود. بنابراین با توجه به حساس و شکننده بودن اکوسیستم های منطقه زاگرس جلوگیری از جنگل زدایی به شدت توصیه می گردد.

    کلیدواژگان: تغییر کاربری اراضی، کیفیت خاک، بازفت
  • صدیقه صلواتی نیک، سعید سعادت*، محسن علامه صفحات 721-735

    منطقه مورد مطالعه در بخش غربی استان خراسان رضوی قرار دارد و دربرگیرنده شهر ششتمد و دهستان های آن است. تنوعی از واحدهای سنگی رسوبی و آذرین که عمدتا منسوب به کرتاسه و یا جوان تر می باشد، در این منطقه رخنمون دارند. وجود رخساره های سنگی مختلف همراه با فعالیت های معدن کاری، صنعتی و کشاورزی می توانند زمینه های لازم برای آلودگی خاک به عناصر سنگین را فراهم نمایند. در این مقاله با توجه اهمیت سلامت خاک از دیدگاه زیست محیطی، حضور و پراکنش این عناصر در رسوبات منطقه مورد بررسی قرار گرفته است. هدف از این بررسی تعیین میزان و نحوه توزیع فلزات سنگین بر اساس نقشه های پهنه بندی عناصر و همبستگی بین آنها در محیط خاک بود. برای دستیابی به این هدف، نتایج تجزیه شیمیایی 1248 نمونه خاک و رسوب آبراهه ای با استفاده از روش های آماری چند متغیره و شاخص های فاکتور غنی شدگی (EF)، زمین انباشتگی (Igeo)، ضریب آلودگی (CF) و شاخص آلودگی (PI) مورد بررسی و تفسیر قرار گرفت. بر اساس ارزیابی های صورت گرفته، کبالت با نیکل و کروم همبستگی خوب و مثبت نشان می دهد که حاکی از منشاء مشترک و احتمالا مرتبط با واحدهای سنگی مافیک است. عناصر سرب و روی نیز با یکدیگر و همچنین با کبالت و وانادیوم همبستگی مثبت نشان می دهند، درحالی که آرسنیک همبستگی منفی با اکثر این عناصر نشان می دهد که حاکی از منشاء جداگانه برای این عنصر در مقایسه با سرب و روی، مس، نیکل و کبالت است. بر اساس شاخص آلودگی، آرسنیک در جنوب و بخش هایی از غرب منطقه دارای آلودگی بالایی بوده و در بقیه مناطق فاقد آلودگی است و یا آلودگی پایینی نشان می دهد. بر اساس ضریب آلودگی، بخش های مرکزی و جنوب غرب منطقه دارای آلودگی متوسط کروم است. بررسی های انجام شده حاکی از خطر حضور آرسنیک بالا در رسوبات رودخانه ای بخصوص در بخش های جنوبی منطقه است. عناصر مس، وانادیوم، آنتیموان، سرب، روی و کبالت فاقد آلودگی قابل توجه بوده و بعید است با غلظت فعلی مشکلات زیست محیطی خاصی را ایجاد نمایند. نتایج حاصل از مطالعات این پژوهش حاکی از آن است که آلودگی های فلزات سنگین در منطقه زمین زاد و عمدتا ناشی از سازندهای زمین شناسی است و آلودگی های انسان زاد، باستثنای فعالیت های معدن کاری در رابطه با عنصر مس، در دیگر موارد نقش موثری نداشته اند.

    کلیدواژگان: شمال شرق ایران، فاکتور آلودگی، فلزات سنگین، محیط زیست، ضریب غنی شدگی
  • سمانه عبداللهی*، احمد گلچین، فاطمه شهریاری صفحات 737-754

    اسیدهای آلی از جمله ترکیبات طبیعی هستند که از ریشه گیاه ترشح می شوند و می توانند حلالیت و جذب فلزات سنگین را تحت تاثیر قرار دهند. به منظور بررسی تاثیر باکتری های محرک رشد گیاه بر تولید اسیدهای آلی و جذب فلزات سنگین توسط ارقام مختلف کلم یک آزمایش فاکتوریل در قالب طرح کاملا تصادفی در گلخانه تحقیقاتی دانشگاه زنجان اجرا گردید. فاکتورهای آزمایشی شامل سه رقم کلم (کلم زینتی، کلم بروکلی و کلم برگ) و شش سطح تلقیح با باکتری های محرک رشد گیاه‎ شامل Pseudomonas putida PTCC1694، Bacillus megaterium PTCC1656، Bacillus subtilis PTCC1715،Proteus vulgaris PTCC1079 ، Azotobacter chroococcum و یک تیمار بدون تلقیح بود. نتایج تجزیه واریانس داده ها نشان داد که نوع رقم، تلقیح با باکتری های محرک رشد گیاه و اثرات متقابل آن ها تاثیر معنی داری در سطح احتمال یک درصد (01/0>p) بر غلظت اسیدهای آلی خاک ریزوسفری، عملکرد تر و خشک گیاه، غلظت سرب و کادمیوم ریشه و بخش هوایی گیاه کلم داشتند. مقایسه میانگین ها نشان داد که تولید اسیدهای آلی در منطقه ریزوسفری، حلالیت و غلظت فلزات سنگین در گیاهان را افزایش داد. به طوری که بیش ترین غلظت اسیدمالیک و سیتریک در خاک ریزوسفری تلقیح شده با باکتری P. putida مشاهده شد. بیش ترین غلظت سرب و کادمیوم ریشه و بخش هوایی گیاه کلم نیز در همین تیمار به دست آمد. هم چنین بیش ترین غلظت اسید استیک، بیش ترین عملکرد گیاه کلم، بیش ترین غلظت کربن آلی محلول و کمترین اسیدیته خاک ریزوسفری مربوط به تیمار تلقیح شده با باکتری B. megaterium بود.

    کلیدواژگان: اسیدآلی، استیک اسید، ریزوباکس، سیتریک، مالیک
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  • Mohammadhasan Naderi, M. Salarijazi Pages 515-532
    Introduction

    The field of ecohydraulics is rapidly growing as the society requires a better understanding of the interrelations amongst the dynamics of the physical processes pertaining to aquatic ecosystems and the modifications observed in their habitat as well as the biological responses of the organisms. Environmental flow science is a common tool for assessing the consequences of changing the flow regime of aquatic ecosystems and providing a minimum flow of aquatic species protection. Environmental Flows assessment is a global challenge involving a number of tangible and intangible segments of hydrology, hydraulics, biology, ecology, environment, socio-economics, and several other branches of engineering including water resources management. River impoundment (dams, weirs), water diversions and consequent modifications to flow regimes have highly destructive effects on aquatic species and ecosystems.    

    Materials and Methods

    In this research, two most common hydrologic methods Tennant and FDC Shifting were compared with a habitat simulation method i.e. PHABSIM. Tennant method is the most popular hydrological method in rivers and is based on the historic flow data. Investigation of the relationship between hydrologic approaches and physical habitat simulation approach and presentation of new recommendations based on the ecological and hydrological data can be very useful for estimating environmental flow in planning phase of river projects. We used river habitat simulation program to model the depth and velocities around boulder clusters to evaluate the habitat for Capoeta habitat in Zarrin-Gol River. The Zarrin-Gol River is one of the rivers in Golestan province in northern Iran. The statistics required for hydrologic calculations were also collected from Zarrin-Gol hydrometry station during the 42-year statistical period (1353-1395). In this regard, after the field studies and the development of the habitat suitability model for the target species, the Habitat simulation of the flow was carried out and eventually the ecological flow regime was extracted. In order to identify the important habitat variables and assess their impact, the life pattern of fish species was divided into juvenile and adult life stages.

    Results and Discussion

    Based on ecological assessment, the environmental water requirement of Gharahsoo river is 30% of mean annual flow for spring and summer and 10% of mean annual flow for autumn and winter seasons. It was found that application of Tennant and FDC Shifting methods led to dramatically low discharges as fixed minimum environmental flows, while habitat simulation method gave an acceptable estimation of ecological regime. However, habitat simulation technique assesses the allowable value of extraction from river flow dynamically, considering the ecological condition and average intermediate values. River conditions including flow velocity, water depth and river bed substrate are combined to form unique habitats facilitating the survival and growth of fish species populations.  Habitat forms are observed in a wide range of rivers depending on the diet and the river type such as Pool, Riffle and Run. The destruction of the Riffle substrate causes disruption and impacts the biological integrity of the current. According to the Q-WUA curve of the Riffle habitat in high waters and flood conditions, the area available for juveniles of the target species decreases because of the flood, morphology and habitat of the river, so large and continuous floods inhibit the opportunity to rebuild habitats from the river and endanger the lives of fish. One of the factors limiting the desirability of the habitat and thus reducing the available habitat in low river flows is the low flow velocity, as well as high stream flow flows. The maximum and minimum flow regime, required to maintain the Zarrin-Gol river ecosystem according to ecological needs, was 2.49 and 0.58 m3/s in April and November, respectively, with an average value of 1.25 m3/s (59 % of natural stream of the river). In the next step, habitat suitability distribution along the stream was investigated. This was performed for the full range of discharges. Habitat suitability distribution along the stream at different discharges indicated that the upstream part of the stream had the poorest habitat condition and moving towards the downstream parts, the habitat suitability condition was improved.

    Conclusion

    Application of the Tennant method based on a hydrological system can be an inappropriate choice for determining the minimum flow to maintain the ecological environment of the river. According to the results, the PHABSIM model can simulate flow, habitat suitability of target species and the habitats dynamics accurately, which is highly required to protect the proper habitat of fish in river ecosystems.

    Keywords: Environmental flow, Habitat simulation, Hydrological methods, Zarrin-Gol river
  • Abdorrahim Firoozi, Seyed Majid Mirlatifi*, Hamed Ebrahimian Pages 533-547
    Introduction

    Agriculture consumes a large portion of groundwater resources. In order to understand the status of groundwater resources in a basin and to optimize its management, it is necessary to carry out an accurate examination of the fluctuations in the groundwater levels. Recharging groundwater aquifers is one of the main strategies for water resources management which its accurate estimation plays a crucial role in the proper management of ground water resources. That portion of the excess irrigation water which becomes in the form of deep percolation should not be considered as wasted water, if its quality is not adversely reduced and it enters and recharges groundwater aquifers. The question is whether deep percolations resulting from irrigating farms with low application efficiencies and poor irrigation management in the Urmia basin would finally recharge ground water aquifers or not. In order to provide a solution to the aforementioned question, after calibrating HYDRUS-1D model, it was used to estimate the fluctuations of the levels of the water tables as a results of irrigations or rainfalls in a number of wheat, barley and sugar beet fields located in Miandoab and Mahabad regions where all agricultural practices were managed and carried out by the local farmers.

    Materials and Methods

    In order to ascertain the effects of irrigation on the groundwater recharge, the required field data was collected from nine agricultural fields including one wheat farm, three barley farms, and three sugar beet farms, all located in the Miandoab region and two wheat fields located in the Mahabad region. All the water balance parameters for each one of the fields were measured in the studied fields, including the depth of irrigation at each irrigation event by using WSC flumes. The Surface runoff from the studied farms was considered as negligible, since all the fields were irrigated using closed end borders. The evapotranspiration of wheat, barley and sugar beet were calculated in the regions using the CROPWAT8.0 model.The soil texture of each of the study fields were determined by hydrometric method in the laboratory and then soil hydraulic parameters were estimated by ROSETTA model. The soil moisture of all the fields during the growing season were measured using a PR2 moisture meter instrument measuring soil moisture at various depths up to  105 cm below the soil surface. The amount of deep percolation occurring during the growing season was simulated by the HYDRUS-1D model. The soil water content measured by PR2 (Delta-T Device) probe were used for HYDRUS-1D model calibration and validation using the inverse solution method. Because of the occurrence of rainfall, irrigation and evapotranspiration, the atmospheric boundary condition was selected as the upper boundary condition and free drainage was considered as the lower boundary condition in order to estimate the groundwater recharge, assuming that water passes through and below the root zone. In areas with shallow ground water depth, constant flow with zero flux was chosen as the lower boundary condition in order to determine the fluctuations of the ground water level. Since the groundwater level in this case study was shallow, zero flux was considered as the lower boundary condition. The soil moisture content before irrigation was selected as the modelling initial condition.

    Result and Discussion

    The HYDRUS-1D model was calibrated by comparing the model estimated soil moisture contents with the corresponding measured values which indicated the coefficient of determination (R2) and root mean square error (RMSE)  values ranging from 0.6 to 0.85 and 0.17 to 0.033 (), respectively.  Another set of measured soil moisture data which was collected by using PR2 instrument and was not used for calibrating the model, was applied to verify the model simulation of the soil moisture content. Comparing the measured and simulated soil moisture contents at this verification stage resulted in coefficient of determination (R2) and root mean square error (RMSE) values ranging from 0.62 to  0.88 and 0.002 to 0.023 (), respectively. There was no significant difference between the predicted and measured soil moisture data in all the fields (P-value> 0.05). The minimum and the maximum coefficient of determinations in the validation stage were obtained in the T5 field with a silty loam soil and in the H3 field having a sandy loam soil. The accuracy of the model performance after it was calibrated and verified using the collected field data, was appropriate for estimating the soil water content during the growing season. The model was used to simulate the soil water contents from the soil surface to the depth of the water table during the growing season to evaluate the degree of aquifer recharge if any happened. The soil moisture front advanced to a depth of 0.7 m below the soil surface in the M1 field and to 4.7 m in the T1field. The amount of groundwater recharge varied from field to field depending on each field’s soil type, cultivation and irrigation management including the depth and the time of the irrigations. The amount of groundwater recharge increased by decreasing crop evapotranspiration. The percentage of ground water recharge in N1, M1 and M2 fields due to limited availability of water resources which resulted in deficit irrigation was very low. The irrigation water requirements estimated by the CROPWAT model for the aforementioned fields were more than the depths of the irrigation water applied by the farmers. The CROPWAT model estimated the irrigation water requirements during the growing season for wheat, barley and sugar beet in the Miandoab region to be 308, 273 and 736 mm, respectively. However, the depths of irrigation applied to such farms ranged from 306 to 500 mm. 

    Conclusion

    This research was conducted to ascertain the effects of local farmer’s irrigation management practices considered as poor management in some areas with plenty of water resources available and rainfall on the amount of the groundwater recharge occurring in the regions studied located in the Lake Urmia basin. The simulated groundwater recharge by the HYDRUS-1D model indicated that the amount of recharge varied from field to field depending on soil type, cultivation and irrigation management practices. In all the fields, the highest amount of groundwater recharge occurred when the crop evapotranspiration was low and therefore, enhancing deep percolation to take place. The highest percentage of groundwater recharge was 28% of the sum of the irrigation and rainfall depths which occurred in the barley field (H3).

    Keywords: Groundwater level, HYDRUS, irrigation, recharge, simulating
  • Nader N. Kouhi Chelle Karan, Hossein Dehghanisanij*, Amin Alizadeh, Elahe Kanani Pages 549-563
    Introduction

    Drought is one of the factors that threatens the performance of agricultural products, especially corn in most parts of the world. Under conditions of water scarcity, the effectiveness and efficiency of fertilizer use is reduced, especially if fertilizer application is not consistent with plant growth. Among fertilizers, nitrogen is one of the most important nutrients for corn, and consumption management of this fertilizer has great importance in order to succeed in increasing the production of corn. Therefore, in conditions of water shortage, balanced and optimal use of fertilizer should be considered to achieve increased yield and water use efficiency.

    Materials and Methods

    This study was conducted to investigate the effect of drip irrigation regimes and different levels of nitrogen fertilizer on yield and yield components of corn and soil moisture changes at the Shaheed Zendrh Rouh Jupar in Kerman province during the years of 2012-2014. The experiment was arranged as a split-plot design based on randomized complete block design with five irrigation regimes (I1 = 100, I2 = 80 and I3 = 60% ETc) as the main-factor and five nitrogen fertilizer level N1 = 0, N2 = 50, N3 = 100, N4 = 150 and N5 = 200 kg/ha) as sub-factor. According to the Kerman Meteorological Station, this region has a semi-arid climate with warm summers and mild winters. To calculate the volume of water consumed, potential evapotranspiration (ETo) was determined using daily meteorological information and Penman-Monteith method (PM). A sampling method was used to measure moisture at different depths of soil.

    Results and Discussion

    The results showed that the highest yield was due to I1 treatments with 8.85 t/ha, and there was a direct relation between crop reduction and water requirement reduction at all stages of crop production. High nitrogen application had a negative effect on yield. Typically, in soils that lack nitrogen, corn grain yield increased with nitrogen addition. However, after reaching the maximum yield, nitrogen addition has no effect on increase or yield may reduce. The interactions of different levels of water and fertilizer showed that I1N4 and I3N1 treatments had the highest (10.6 ton/ha) and lowest (1.24 ton/ha) value of corn yield, respectively. The highest and lowest grain yield components (thousand grain weight, number of kernels row, number of kernels per row, cob length, cob diameter) were observed in N1 and N3 I1 treatments, respectively. The highest water use efficiency (1.26 kg/m3) was observed in I2N4 treatment and the lowest (0.068 kg/m3) in I3N1 treatment. The results of this study showed that the remaining moisture content in soil decreased by decreasing amount of irrigation water and nitrogen fertilizer in 20 days after planting. At 75 days after planting, reasons such as severe water shortages during growth, reduced root density, high water requirement at this stage of growing season, and the plants need to nutrients have probably caused the roots to absorb as much as possible of the top three water and nutrient. As a result, the moisture that reaches the last layer is less. The results showed that in the last stages of growth compared to other stages, the plant water requirement is reduced and excess water penetrates the lower layers.

    Conclusion

    According to the results of this study, nitrogen fertilizer at 150 kg/ha with 100% water requirement is the best combination for corn farming in semi-arid climates.

    Keywords: Different fertilizer levels, Irrigation regime, Soil moisture, Surface drip
  • B. Sarcheshmeh*, Javad Behmanesh, Vahid Rezaverdinejad Pages 565-577
    Introduction

    Drying Urmia Lake, located in northwest of Iran, is mainly related to the reduction in rivers flowing into the lake and hydrological parameters changes. Considering the importance and critical ecological conditions of Urmia Lake, the purpose of this research is to accommodate the environmental water requirement in managing rivers leading to the lake, including Zarrinehrood as the largest river to the lake. Moreover, water scarcity was assessed by QQE approach in this basin.

    Materials and Methods

    Tennant method is easy, rapid, inexpensive, and is based on empirical relationships between the recommended percent of the MAF. The ecological conditions of the river have been determined for use in this method. In this study, different levels of EFR were calculated to protect the relevant levels of habitat quality defined in the Tennant method. Also the fraction of Blue Water Resources (BWR) required to protect a “good” level of habitat quality was considered as the suitable EFR. If it is less than the lower limit, the habitat quality will be in degraded status. SQQE is a complete index to demonstrate water scarcity by considering water quantity and quality and EFR indicator. The Smakhtin method provided an indicator for assessing the water scarcity. WSI = Where WSI is the index of water scarcity, MAR is the mean annual flow and EWR is the environmental water requirement of river. If the water scarcity index is more than one, the river would suffer from water shortage and not be able to meet the environmental water requirement. When the water scarcity index is between 0.6 and 1, the river would be under stress, and if it is between 0.3 and 0.6 Harvesting conditions from the river is moderate, and if it is less than 0.3 the river is ecologically safe and has no shortage.

    Results and Discussion

    According to the Smakhtin method, can be noticed that the calculations of this method are the same quantitative index of the other method used in this research. Only the quantitative conditions are evaluated in the Smakhtin method. However, in addition to the quantity (blue water footprint), environmental requirement and water quality are also included in the other method used in this research. Figure 1 shows the mean annual flow (MAF) and environmental flow requirement (EFR). As shown in figure 1, the majority river flow has been conducted from January to June and the rest from July to December. The annual BWR in the Nezamabad station was equal to 1208 × 106 (m3/year). To protect the habitat health of Zarrinehrood river at a good level, 400×106 (m3) of water must be left in the river per year. Therefore EFR was equivalent to 33.11% of the annual BWR. It is about one-third of total BWR.In this station, EFR ranged from 60×106 (m3/year) as severely degraded to 2400×106 (m3/year) as maximum habitat health situation by using the Tennant table (Fig 2).Figure 1- Environmental flow requirement (EFR) and mean annual flow (MAF) for the (Nezamabad station) Zarrinehrood river basin Figure 2- Different levels of total environmental flow requirement (EFR) in the (Nezamabad station) Zarrinehrood river. Habitat quality levels with the flows shown in table 3 (Tennant) have be matched The BWF and the BWA for the studied station were calculated 830×106 and 808×106 (m3/year), respectively. The BWF is 1.02 times the BWA. Therefore, the WSI Smakhtin and S Quantity will be 1.02.  The total GWF in this station was 1.08 times the BWR. Thus, the S Quality will be 1.08. P is a demonstrator that shows the percentage of EFR in total BWR. It is related with the EFR to protect the habitat quality in a “good” level. As you know, the number in the bracket shows that 33.11% of the total BWR of the basin is required as EFR, for maintaining the ecological habitat condition at the ‘good’ level. Other percentages of EFR are used to represent other ecological levels of habitat condition. The S Quantity and S Quality for the Nezamabad station in Zarrinehrood river basin were obtained 1.02 and 1.08, respectively. Both indices are above the threshold (1.0), and the basin suffer from both qualitative and quantitative deficiencies. Thus, the final water scarcity indicator, SQQE, is 1.02 (33.11%) |1.08.

    Conclusion

    The EFR for protecting the good ecological level is not enough in some months during a year. Water scarcity was evaluated by simultaneously considering water quantity, water quality and EFR in the Zarrinehrood river basin in Iran. Compared with the Smakhtin method as another method of water scarcity assessment, the Smakhtin Index is only quantitatively, but the SQQE Index provides a comprehensive assessment of the water scarcity. The results imply that the studied region is suffering from both water quantity, water quality problems. The water pollution has a big role in causing the water scarcity in the river basin. This shows that only aiming on reducing water consumption cannot help impressive reduce the water scarcity. It is necessary to pay attention to reduce water pollution and water conservation. Even in the areas that the hydrological and ecological data are rare, the QQE approach as a holistic method could be used.

    Keywords: Environmental Flow Requirement, Water quantity, Water quality, Water scarcity, Zarrinehrood
  • D. Rahimi*, H. Yazadnpanah Pages 579-592
    Introduction

    Statistical models and numerical simulations have been widely used to detect relationships between the climate and crops. However, the influence of non-climatic factors (such as cultivar and fertilizer changes on yield crop needs to be eliminated. For this reason, dynamic crop models include the SUCROS, Erosion Productivity Impact Calculator(EPIC), WOrld FOod STudies (WOFOST), Agricultural Production Systems sIMulator (APSIM), and Decision Support System for Agrotechnology Transfer (DSSAT) have been used in water, nitrogen and weather responses. Among these models DSSAT contains separate models for different crops and can quantitatively predict the growth and production of the annual field crops.

    Materials and Methods

    In this study, the data of Shahrekord Agricultural Meteorological Station and the data of Lysimeter Station were used to evaluate the correlation between the research results and Lysimeter data from Pearson correlation coefficient, and the RMSE, MAD and MSE are applied in order to calculate the error.

    Results and Discussion

    Lysimeter: The wheat evapotranspiration amount from the planting (20 of Octobers) to the harvest time (14 of July) is recorded as 611.24 mm. Precipitation during the winter is low but continuous and it is 127 mm that equivalent to the evapotranspiration at this time of growth. In the warm season, a quarter of the evapotranspiration is provided by rainfall. The average of winter evapotranspiration is 0.87 mm per day and in the growth season is 4 mm per day. Also from planting to harvest is 2.42 mm per day that is recorded its maximum 7.8 mm and its minimum 2.32 mm per day. The total amount of drained water during the growth is 76.04 mm that 8.8% of the total rainfall. It indicates that drainage water from the soil is low and irrigation has a high efficiency. CERES-WHEAT  Wheat evapotranspiration amount during the growth period is 413.51 mm by FAO Penman-Monteith and 489.53 mm by Priestley-Taylor. Precipitation during the winter is low but continuous and it is 127 mm that equivalent to the evapotranspiration at this time of growth. In the warm season, a quarter of the evapotranspiration volume is provided through rainfall. The average of winter evapotranspiration based on the F.P.M and P.T methods are 0.86 and 1.23 mm/day and in the growing season 2.98 and 3.11 mm/day, respectively. During the experiment, the evapotranspiration average is 1.59 mm/day for the FPM method that the maximum is 6.61, and the minimum is 0.379 mm/day. This amount is 1.88 mm/day for P.T method which the maximum is 5.64 and the minimum is 0.45 mm per day. The total amount of drained water during the growing period is 106.3 mm, based on the F.P.M method and 90.2 mm based on the P.T method.The correlation between farm data and the data obtained through the F.P.M method of CERES-Wheat model is 0.97, which for the P.T method is 0.92. The MAD, MSE and RMSE values obtained between the F.P.M method and farm data are 0.95, 0.95 and 1.57, respectively, and for the P.T method, 0.97, 1.47 and 1.21, respectively. With respect to correlation and MAD, MSE and RMSE value, it is found that the model is highly capable in simulating evapotranspiration and crop performance. Among the methods applied in determining evapotranspiration, the F.P.M method with high correlation and lower error value is more accurate than the P.T method.Water Factor: From the day 177 to 216 is considered the most sensitive stage of plant growth. Based on DSSAT output over a 25-day period (196 to 216 days) the water available is severely depleted and the plant may experience drought stress. At this stage of the growth, water deficiency should be offset by increasing the time and the amount of irrigation.Day 210 is the beginning time of the increase in evapotranspiration of the plant. During this period, the amount of water which is uptake from the soil was less than 1 time the plant demand. This period of stress was based on the FAO Penman- Monteith method between the 203rd and 210th days. During this period, the plant goes through its clustering and flowering stages, and water stress at this stage causes the growth of wrinkled and lean grain, resulting in reduced grain weight and reduced crop yield. Water scarcity must be compensate by increased irrigation.

    Conclusion

    Comparison of model calibration results and farm data indicates that there is a high correlation between farm data and model output. The error between the model results and the Lysimeter station data is low. Among the methods used to calculate the evapotranspiration in the model, FAO Penman- Monteith method is the highest correlation and the lowest error value with the farm experiments and results. In general, the results indicated that the CERES-Wheat model has a high ability to simulate evapotranspiration and wheat yield. Regarding observed data for crop irrigation program indicates that farmers' performance in managing the amount of water needed for the crop at various stages of the growth was not optimal. Consequently, drought stress was observed for developmental and mid-growth stages. The DSSAT simulation indicated that the optimal irrigation management adjusts the time and value of irrigation water according the actual evapotranspiration and water requirement would significantly improve irrigation water use.

    Keywords: DSSAT-CERES-WHEAT, Evapotranspiration, FAO Pennman Monteith, LySimeter, Priestley- Taylor
  • N. Mehrab*, Mojtaba Norouzi Masir, Mostafa Chorom Pages 593-608
    Introduction

    Decontamination of heavy metals (HMs), especially cadmium (Cd) which has high mobility in the soil, is very important due to the effects of HMs pollution on the soil, environment, and human. Numerous efforts have been made to develop technologies for the remediation of contaminated soils, including ex-situ washing with physical-chemical methods, and the in-situ immobilization of metal pollutants. These methods of clean up are generally very costly, and often harmful to properties of the soil (i.e., texture, organic matter, microorganisms). Recently, the phytoremediation of HMs from contaminated soils has attracted attention for its low cost of implementation and many environmental benefits. Several chelating agents, such as DTPA, EDTA, and NTA, have been studied for their ability to dissolve metals, leach heavy metals, and enhance the uptake of metals by plants. Although many researchers have reported that EDTA is excellent solubilizing agents for HMs from contaminated soils, it is quite persistent in the environment due to the low biodegradability. Hence recently the easily biodegradable chelating agent NTA has been proposed to enhance the uptake of HMs in phytoremediation as well as the leaching of HMs from the soil. Therefore, in the present study attempts are made to investigate the effect of applicability NTA in Cd leaching and the refining of Cd from contaminated-soil by maize.

    Materials and Methods

    In this research, the effect of NTA on Cd leaching and its absorption by maize in contaminated-soil in a greenhouse experiment were investigated. The experiment was a factorial experiment based on a completely randomized design. The treatments consisted of three levels of Cd contamination (0, 25 and 50 mg kg-1soil) and three levels of NTA (0, 15 and 30 mmol per pot) in loamy soil and in the cultured and non-cultured conditions under three irrigation conditions. The soil was contaminated with cadmium chloride (CdCl2.2.5H2O). Nitrogen, phosphorus, and potassium (in the form of urea, triple superphosphate and potassium phosphate, respectively) were added to the pots. NTA was added in three steps to the pots. The first step of adding NTA was beginning 4 weeks after cultivation, occurring approximately once in 14 days. Also, 7 days after adding NTA, the pots were irrigated with an amount corresponding to 20% more water than the moisture of soil saturation condition. The drainage water collected from each irrigation event was kept in a refrigerator at 5°C prior to Cd analysis. The plants were cut about 5 mm above the soil surface after 10 weeks of maize growth and were dried for analyzing Cd in the plant. Analysis of variance was used to study the effects of different treatments of Cd and NTA on Cd contents in drainage water, plant, and soil. Statistical analysis were performed using SPSS. Means of treatments were compared using Duncan’s Multiple Range Test (DMRT) and the graphs were plotted in Excel.

    Results and Discussion

    The contrasting impact between irrigation rounds and Cd treatments, as well as NTA treatments on Cdtotal leached was significant (P<0.05). The highest Cd leached was in 50 mgCd kg-1soil (Cd50) and 30 mmol NTA (NTA30) in the first irrigation round. In the next two rounds, the Cd leached from the soil was inconsiderable. Different levels of Cd and NTA showed a significant difference in Cd concentration in the first round of leaching.  In non-cultivated pots, the amount of Cd leaching in Cd50NTA15 and Cd50NTA30 treatments increased by 8 and 15 times, respectively than that in Cd50NTA0 treatment. In the case of similar treatments in the presence of maize, the Cd leaching rate increased by 5.8 and 6 times, respectively, than that in (NTA0). Cd absorbed by maize in (Cd50, NTA30) was maximum and that measured 58% more than that in (Cd50, NTA0), while dry weight decreased significantly (30% in the shoot and 40% in the root). After the cultivation and leaching process, the maximum amount of DTPA-extractable Cd was observed in (Cd50, NTA0). While using (NTA15, NTA30) at the same level of Cd-contamination (Cd50), there was a significant decrease in DTPA-extractable Cd (due to the increase in Cd dissolved, Cd leached and Cd absorbed by plants). Due to pH between 2-3 and EC about 2.5-3.5 in NTA solutions, the application of NTA in soil decreased pH and increase EC in the soil. On the other hand, the decrease in pH of soil increased solubility of calcium carbonate equivalent (CCE), thereby reduced CCE in the soil. The results of this study showed that the soil pH was effective on HMs absorption by plants, therefore the availability of Cd after the use of NTA may be due to the decrease of alkalinity in the soil. The presence of organic-metal bonds in chelate-metal compounds causes metals to be less exposed to colloids, hydroxides, and oxides thus will prevent their stabilization in the soil. So it can be said that one of the effective methods for increasing the absorption of HMs from the soil by the plant is to reduce the pH of the soil. Some of the soil properties, such as pH and total heavy metal concentration, improves the efficiency of the chelator agent.

    Conclusion

    The results showed that an increase in the amount of Cd contamination and NTA applied increased Cd content in drainage water and Cd which was uptake by maize. Also, results showed well, the combined of maize planting and the use of NTA is successful in refining Cd from contaminated-soil. It seems that Adding NTA as a natural chelator in Iranian calcareous soils can increase the dissolution of Cd and extract it from the soil during a leaching period without contamination of the environment, as well as increase the efficiency of removing Cd by maize.

    Keywords: Leaching, NTA, Phytoremediation, Cadmium
  • hossein Bagheri, Azizallah Izady Pages 609-622
    Introduction

     Vermicompost is a type of biological organic fertilizer obtained from earthworm activity. Vermicompost is used in sustainable agriculture due to its beneficial effects on diversity of plant nutrients and physical-hydraulic modification of soil. However, high presence of solutes in the structure of vermicompost causes soil salinity, increases soil sodium content and changes soil pH. Soil flushing is one of the well known strategies to minimize the mentioned disadvantages of vermicomposting. Although flushing can reduce the soil salinity and sodium content, it leads to transportation of some soil substances such as nitrate, dissolved organic carbon and colloids which their tracing is necessary because of soil quality monitoring and possibility of water resources pollution. The objective of the current study was to investigate the effects of vermicomposting on soil chemical, physical and hydraulic properties and its role on the amount of soil total dissolved salts (TDS), sodium, nitrate, dissolved organic carbon and leaching behavior of colloids.

    Materials and Methods

    To treat the soil, 1.45 weight percent of vermicompost (17.68 tones/hectare) was mixed with regular soil. Physical, chemical and hydraulic properties of soil were determined. PVC columns with length of 20 cm and internal diameter of  5.95 cm were used and filled with soil to perform leaching during 24 hrs in saturated condition  experiment. The effluent of columns were collected at various interval times, and their sodium, nitrate, dissolved organic carbon, TDS and colloid contents were measured and the cumulative amounts of them were calculated at 6 and 24 hrs. All experiments were carried out in three replications, and the mean comparison of leaching parameters was done according to Duncan's multiple range test at probability level of 5%.

    Results

    Vermicompost increased the studied soil chemical properties i.e, organic matter, organic carbon, extractable nitrate, soluble sodium, soluble and exchangeable sodium, EC and TDS to 12.42, 12.9, 118.96, 80.43, 44.48, 109.4 and 109.4 %, respectively and decreased soil pH to 2.35 %. Soil bulk density reduction to 3.81 % and enhancement of soil porosity, saturated hydraulic conductivity and the pore water velocity to 1.38, 7.25 and 5.6 %, respectively are the other results of vermicompost application. The used vermicompost fertilizer caused displacement of soil water retention curve to more moisture around of saturated and permanent wilting points and reduction of air entry potential. In this regard, vermicomposting increased all of soil hydraulic coefficients of van Genuchten model including θr, θs, α and n, and its effect was specially more on θr and α. The result of leaching experiments showed that the amounts of leached TDS, sodium, nitrate, dissolved organic carbon and colloid in vermicompost-containing soil during 6 hrs were 491.4, 65.22, 116.71, 47.68 and 24.86, and during 24 hrs were 946.3, 72.16, 146.26, 95.11 and 41.97 mg/Kg, respectively. For the natural soil, these amounts during 6 hrs were 240.9, 11.84, 20.08, 23.2 and 15.11, and during 24 hrs were 665.6, 15.69, 44.48, 58.34 and 29.39 mg/Kg, respectively. Therefore, vermicompost significantly increased the amounts of leached TDS, sodium, nitrate, dissolved organic carbon and colloid, because of containing more contents of solute, sodium, nitrate and organic matter in its structure. It also increased the porosity and hydraulic conductivity of soil, and made changes in soil water retention curve (P<0.05). The presence of more sodium in vermicompost together with its effect on soil porosity enhancement increased the colloid dispersion and consequently its leaching. In addition, the leaching rate of all of parameters at 24 hrs in comparison to 6 hrs decreased significantly due to high amount of solute leaching through mass flow at initial time of leaching experiment and leaching residual solute by time-consuming process of diffusion.

    Conclusion

    Although vermicompost can enriched the soil due to increasing nitrate and organic matter contents, it leads to soil salinity and increases sodium contents. Flushing the soil treated by vermicompost removed the amounts of TDS, sodium, nitrate to 10.4, 76.2 and 44.6 % during 24 hrs. Therefore, leaching had a considerable effect on soil sodium reduction and a little effect on soil salinity reduction. Moreover, in comparison to chemical fertilizers, the high nitrate fraction of applied vermicompost resulted in sustainability of soil fertility. It is expected soil salinity and nitrate leaching fraction of vermicompost will be reduce by managing leaching methods, treating vermicompost before using and reducing fertilizer application rate. Thus, the results of current study warn the farmers who used vermicompost in soil to control the soil salinity, ground water pollution and vertical colloid migration.

    Keywords: Soil hydraulic coefficients, Soil water retention curve, Dissolved organic carbon leaching, Nitrate leaching, Colloid leaching
  • E. Mehrabi Gohari, H.R. Matinfar*, R. Taghizadeh Mehrjardi, A. Jafari Pages 623-635
    Introduction

    Soil texture is the most important environmental variable because it plays a very important role in reducing the quality of land and water transfer processes, soil quality control and fertility. On the one hand, soil texture components are the basis of environmental predictive models and digital mapping of soil and on the other hand, soils are temporally and spatially variable, thus distinguish zoning and their monitoring with traditional sampling methods and laboratory analysis is very costly and time consuming. As a result, the development of methods for analyzing the soil and for required information has become very important. Visible and near infrared spectroscopy (VIS-NIR) is widely used to estimate soil physical properties and estimate soil texture. The present study aims to predict soil texture using spectral measurements and artificial neural network models and partial least squares regression.

    Materials and Methods

    The study area in southeastern Iran is approximately 70 km from Kerman. In the study area, based on the hypercube technique, 115 profiles were identified and then horizons were sampled. In this way, for each point of study, the necessary information, including the location of the profile on the ground, the type of geomorphic unit and the type of materiel, were recorded and taken from the horizons of each profile. In all soil samples, after drying and passing through 2 mm soil, the soil texture was measured by hypercube. Spectral radiometer was used to measure the spectral reflection of soil samples. The soil samples were air dried and sieved and then placed in a petri dish with an approximate diameter of 10 cm and transferred to the dark room for spectral analysis. Each specimen was tested four times (for each 90 degree sequential rotation) to remove the effects of a change in the radiation geometry. Soil samples were scanned, and absolute reflections at a spectral range of 2500-350 nm yielded 2150 spectral data points (SDPs) per soil sample with a spectral resolution of one nanometer. Finally, to construct a suitable model for forecasting the percentage of clay, sand, and silt, the least squares model was used with the number of factors 1 to 10 by Artificial Neural Network (ANN) modeling using JMP software Work.

    Results and Discussion

    The reflectance spectrum of the visible range - near infrared - was measured for specimens. Since preprocessing of spectral data has an effective role in improving the calibration, in order to perform spectral preprocessing, two first nodes of the first and the end of the spectra were first removed in the range of 350-400 and 2450-2500 nm. In addition, the interruption due to the change in the detector in the range of 900 to 1000 nm was also eliminated. Types of preprocessing methods were performed on spectral data. Then, using partial least squares regression analysis, the best model was produced when the first derivative was fitted to reflection values. The explanation coefficients for this low and unacceptable model were obtained. Therefore, using partial least squares regression analysis, the best wavelengths were selected to predict the percentage of clay, sand, soil, and extracted from the model. Then it was used as input in the neural network model. To determine the best combination, root error index and error coefficient were used. The results of artificial neural network showed that the number of neurons 9.8 and 10 had the best composition for predicting clay, sand and soil silt. The root-squared error results for clay, sand, and soil silt were 3.42, 6.94, and 4.383 respectively. Also, the results of the explanatory factor were 0.84, 0.83 and 0.81, respectively. After obtaining the optimal structure in the artificial neural network training phase described above, the trained network has been tested on the test data to determine the accuracy of this model to predict clay, sand and silt of surface soil. The root-squared error results for clay, sand and silt components were obtained at 5.54.9.14 and 7.01. Also, the results of the explanatory factor were 0.76.0.70 and 0.73 respectively. The best result of the prediction for partial least squares regression was obtained for the sand sample. The results indicate that the neural network performance is better than partial least squares regression, which is consistent with Mouazenet. al (2010) and also ViscarraRossel R. et. al (2009). Acceptable performance of the artificial-neural network can be attributed to the ability of this model for non-linear behavior of soil texture in visible spectroscopy. In this study, specific wavelengths, which Ben Finder et al. (2003) obtained in the study on the soils of Israel, were used. This conclusion confirms that various types of soil can be modeled using specific wavelengths. The advantage of this study is that, when using the artificial neural network, no pre-processing of reflection data is required before applying the model. Since the relationship between the percentage of soil particles (clay and gravel) and the reflection of the soil is not linear, the neural network method is very useful for analyzing the relationship between soils. Finally, the map of clay, sand and silt and map of soil texture was prepared by artificial neural network method in GIS environment.

    Conclusion

    The results of this study showed that the neural-dynamic network has a better performance than partial least squares regression. Calibration models designed and used in this study can be transported for use with other soils. When the partial least squares regression model was implemented, it had a very low accuracy (R2 ~ 0.1-0.3); on the contrary, the neural network-based method had high accuracy and less error. Note that although neural-dynamic modeling estimates higher precision results from soil texture, both approaches depend on wavelength selections, and so wavelengths should be selected before using any of the two models. To be finally, a meaningful relationship between the selected wavelengths and the percentage of clay, sand and silt in the present study indicates that soil texture is not only possible but also reliable by reflection spectroscopy.

    Keywords: Artificial neural network, Infrared, Modeling, Prediction, Partial least squares regression, Visible spectroscopy
  • H. Hosseini*, M. Fekri, M.H. Farpoor, M. Mahmoodabadi Pages 637-648
    Introduction

    The availability of the applied phosphorus (P) is controlled by sorption-desorption reactions in soil. Since the sorption-desorption reactions are affected by physical and chemical properties of the soil, the presence of organic matter (OM) and carbonates can also effect on the P sorption capacity in soil. The purpose of this study was to investigate the effects of OM and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province.

    Materials and Methods

    Six surface soil composite samples (0-30) were collected from Kerman Province located in southeast of Iran. The soils with a wide range of OM and calcium carbonate were selected for sampling. Samples were air dried and passed through a sieve of 2 mm. Physicochemical properties of the soil samples were determined according to the Soil Survey Laboratory Manual. Thereafter, the soil samples were divided into three parts. One portion was used for treatment with sodium hypochlorite to remove organic matter. The second part was treated with sodium acetate buffer (pH = 5) to remove carbonates. The third was used as a control without any treatment. Batch experiments were carried out to determinthe P-sorption isotherms in soil. The sorption behavior of P was studied by Langmuir and Freundlich isotherm models. All experiments were conducted in three replications.

    Results and Discussion

    The results showed that organic matter and equivalent calcium carbonate, removed from the studied soils with an average efficiency of 86.7% and 84.9%, respectively. Although the isotherms data showed that both Langmuir and Freundlich equations fits to data,Langmuir equation with higher mean of correlation coefficient (R2=0.982) and lower standard error (0.022) showed the best fit to P-sorption data for all soil samples (with and without treatment). Removal of organic matter by sodium hypochlorite increased the phosphorus adsorption capacity in the studied soils. After removal of soil organic matter, an increase in phosphorus adsorption capacity in the studied soils. With respect to control, removing the organic matter increased the adsorption capacity parameters (qmax and kf) about 37 to 104 mg.kg-1 and 11 to 23 L.kg-1, respectively. These results indicate that Fe- and Al-oxides and other available adsorption sites on the mineral surfaces are coated by organic matter and are activated after removal of OM. Removal of carbonates from the soil significantly reduced the P-sorption capacity. qmax and kf were decreased by 17% and 32%, respectively, compared to untreated soils. It is, therefore suggested that available P adsorbing surfaces decreases by removing carbonates from the soil.Constants related with bonding energy increased by 17.03% and decreased by 28.78% by removal of OM and calcium carbonate, respectively. The P maximum buffering capacity is an important indicator for assessing phosphorus stabilization capacity in soil. The greater P buffering capacity, the fewer ability of phosphorus replacement to soil solution. After removal of carbonates, this parameter decreased by an average of 42.5%. The results suggested that carbonates is an important factor in availability of phosphorus in soil. The required phosphorus standard increased by 14.43% by removing OM in the studied soils. However, the removal of carbonates reduced the need of soil for phosphorus by 40.5%.

    Conclusion

    In this study was investigated the effect of removing organic matter and carbonates on phosphorus sorption isotherms in some calcareous soils of Kerman province. The results of this study showed that P sorption capacity is affected by the amount of carbonates and organic matter. Removal of organic matter from the soil increased the sorption capacity of phosphorus due to Fe- and Al-oxides. Other available adsorption sites on the mineral surface which are coated by the organic matter are active. Carbonates is known as an active site for maintaining phosphorus in the soil and its removal from soils reduces the phosphorus adsorption capacity. Applying/Preserving organic matters to/in soil can increases the efficiency of phosphate fertilizer application and improves plant nutrition. The removal of carbonates from the studied soils reduced their need for phosphorus. Therefore, as well as the addition of organic matter to soil, the removal or reduction of carbonates from agricultural soils is important for improving phosphorus utilization efficiency and plant nutrition management.

  • R. Khodadadi, Reza Ghorbani Nasrabadi*, Mohsen olamaee, Seyed Alireza Movahedi Naini Pages 649-660
    Introduction

    Worldwide studies have shown that inappropriate land uses over the past 45 years have resulted in salinization of 6% of the world's land. Salinity has negative effects on soil physicochemical properties and microbial activities. The imbalance in nutrient uptake, ion toxicity and decreasing water consumption due to high osmotic pressure are resulted from high accumulation of solutes in soil solution. One of the strategies to mitigate soil salinity is the inoculation of crops with different types of beneficial soil bacteria and fungi. Plant growth promoting bacteria (PGPB) are a diverse group of bacteria capable of promoting growth and yield of many crops. The most important growth promoting mechanisms of bacteria are the ability to produce plant hormones, non-symbiotic nitrogen fixation, solubilization of insoluble phosphate and potassium, biocontrol of plants pathogens through producing hydrogen cyanide and siderophore production. Plant inoculation with growth promoting bacteria causes an increase in several indices such as shoot fresh and dry weight, root dry weight and volume as well as chlorophyll content. The synergetic effect of Azotobacter and Azospirillum on the plant has been documented by increasing the absorption of nutrients, production of hormones that stimulate plant growth such as auxin, and influencing the root morphology. Due to the wide area of saline soils, appropriate methods to reduce the negative effects of salinity are of great significance. Given the importance of using bacteria adapted with climatic conditions and soil ecosystems in each region, as well as the efficiency of the combined application of growth promoting bacteria, this study was conducted to investigate the effect of growth promoting bacteria as a single and combined application at two levels of salinity calculated based on the threshold of barley yield reduction (Karoon cultivar) and 50 % reduction in barley yield.

    Materials and Methods

    In order to record the Azotobacter isolates, 15 soil samples were collected from salt affected lands of Golestan province. Thirty two Azotobacter isolates were isolated by physiological and biochemical tests and cyst production in old culture. Then, their ability to grow in different concentrations of salinity, drought stress tolerance, polysaccharide production, auxin production, phosphorus and potassium solubilization, hydrogen cyanide synthesis and biological fixation of molecular nitrogen were investigated. Based on physiological and growth stimulation tests, Az13 isolate was selected as the superior isolate of Azotobacter for greenhouse test. Azospirillum superior isolate was then prepared from the microbial bank of Soil Science Department, Gorgan University of Agricultural Sciences and Natural Resources. A soil with 16 dS/m salinity was selected to determine the effects of experimental treatments at two threshold salinity levels of yield reduction and 50 % reduction of barley yield. Then, soil salinity was reduced to 8 dS/m (yield reduction threshold) by leaching. After reaching to the desired salinity, the soil was removed from the pots and air dried. The sample was sifted through a 2 - mm sieve and again transferred to the pots. The barley seeds, Karoon cultivar, were used. To prepare the inoculum, firstly the bacterial isolates were grown in the pre-culture nutrient broth medium, and then incubated at 120 rpm in a shaking incubator at 28°C for 48 hours. Afterwards, each seed was inoculated with one milliliter of the bacterial inoculant with a population of 109 CFU/ml. This experiment was conducted as factorial in a completely randomized design with three replications in the greenhouse at Gorgan University of Agricultural Sciences and Natural Resources. The treatments included four levels of bacteria (without inoculation, Azotobacter inoculation, Azospirillum inoculation, combined inoculation of Azotobacter and Azospirillum) and two levels of salinity (8 and 16 dS/m). After 70 days (late vegetative growth period), some growth and physiological indices and concentration of nutrients uptake were measured.

    Results and Discussion

    The results showed that salinity stress had a significant (p < 0.01) negative effect on growth and physiological traits and nutrient uptake of the plant. The combined application of Azotobacter and Azospirillum bacteria showed a positive significant influence (p < 0.01) on growth, dry weight, and root dry weight in the plant under salinity stress. The combined application of bacteria increased the chlorophyll a, b and a + b content at a salinity level of 16 dS/m by 136.49, 117.86 and 127.97 %, respectively. The combined application of bacteria resulted in a 65.39 and 55.94 % increase in proline amino acid content at salinity levels of 8 and 16 dS/m, respectively. The results revealed that nitrogen, phosphorus and potassium levels increased by 81.97, 80 and 66.67%, respectively, at 16 dS/m salinity level in combined application of both bacteria. Sodium ion accumulation in all bacterial treatments decreased in both salinity levels compared to control treatment and the highest reduction was observed in combined bacterial inoculation. These findings underline the positive effect of bacterial inoculation, particularly their combined application, on the growth and nutrients uptake of barley under salt stress.

    Conclusion

    Our results indicate that increasing salinity level significantly decreased shoot dry weight, root dry weight, plant height, chlorophyll content and nutrient concentrations of barley. Inoculation of salt-resistant bacteria, including Azotobacter and Azospirillum, reduced the adverse effects of salinity on growth and physiological traits, which was more pronounced in Azotobacter than Azospirillum. The combined application of Azotobacter and Azospirillum had a significant effect on root dry weight, plant height, chlorophyll content, increasing nutrient concentration efficiency (nitrogen, phosphorus, and potassium) and decreased sodium concentration at both salinity levels (8 and 16 dS/m) compared with the individually inoculated bacteria. Hence, the application of Azotobacter and Azospirillum isolates is an appropriate method for pot experiments with saline soils. To apply these results, field experiments in saline soils must be carried out to evaluate the effect of these bacterial isolates on the crop growth, yield and physiological characteristics.

    Keywords: plant growth promoting, proline, Salinity, chlorophyll
  • S. Ashrafi Saeidlou, A. Samadi, M.H. Rasouli Sadaghiani*, M. Barin, E. Sepehr Pages 661-673
    Introduction

    Potassium (K) is abundant in soil, however, only 1 to 2 % of Potassium is available to plants. Depending on soil type, 90 to 98% of soil K is in the structure of various minerals such as feldspar (orthoclase and microcline) and mica (biotite and muscovite). About 1 to 10 % of soil K, in the form of non-exchangeable K, is trapped between the layers of certain types of clay minerals. The concentration of soluble K, which is directly taken up by plants and microbes in the soil and is exposed to leaching, varies from 2 to 5 mg l-1 in agricultural soils. Imbalanced use of chemical fertilizers, a significant increase of crop yield (depletion of soil soluble K), and the removal of K in the soil system result in a large rate of K fixation in the soil. As a result, K deficiency has been reported in most plants. The annual increase in the price of K fertilizers and the destructive effects of them on the environment have made it necessary to find a solution for the use of indigenous K of soil. The use of biofertilizers containing beneficial microorganisms is one of these strategies. Although K solubilizing bacteria can be an alternative and reliable technology for dissolving insoluble forms of K, lack of awareness among farmers, the slow impact of K biofertilizers on yield, less willingness of researchers to develop K biofertilizers technology and deficiencies of technology in respect to carrier suitability and proper formulation, are the major reasons for why potassium solubilizing microorganisms and K biofertilizers draw low attention.

    Material and Methods

    The purpose of this study was modeling and evaluating the effects of different vermicompost, phlogopite and sulfur ratios on the solubility and release of K by Pseudomonas fluorescens and indicating the optimized levels of these variables for efficient biofertilizer preparation. 20 experiments were carried out using the response surface methodology (RSM) based on the central composite design and the effect of different values of vermicompost, phlogopite and sulfur variables, in the four coded levels (+α, +1, 0, -1 and -α), was evaluated on K dissolution. The applied vermicompost, phlogopite and sulfur in the experiment were ground and filtered through a 140 mesh sieve and their water holding capacity were determined. According to experimental design, different amounts of mentioned materials were combined and samples were sterilized in autoclave. The required amount of water along with 1 ml of bacterial inoculant were added to the samples. The samples were kept in incubator for 2 months. At the end of experiment, amount of soluble K were measured by the flame photometer.

    Results

    The analysis of variance (ANOVA) depicted the reliable performance of the central composite predictive model of K dissolution (R2= 0.949 and RMSE=0.8). Based on the results, the interaction of vermicompost with sulfur (p < 0.038) and the interaction of phlogopite with sulfur (p < 0.0083) were relatively high and significant. Sensitivity analysis of the central composite design revealed that the vermicompost (X1), phlogopite (X2) and sulfur (X3) had positive and negative impact on potassium dissolution, respectively. Therefore, when sulfur content increased to 91.70%, K dissolution decreased to around 31.61%. According to the prediction under optimized condition, maximum potassium dissolution was obtained at the presence of 41.78, 24.35 and 10.25% of vermicompost, phlogopite and sulfur, respectively.

    Conclusion

    The results indicated that the applied fertilizer composition (vermicompost + phlogopite + sulfur) had a desirable impact on Pseudomonas fluorescens solubilizing ability on a laboratory scale. Due to the fact that Iran soils are often calcareous, there are high amounts of insoluble and unavailable nutrients. Under these unsuitable conditions, the application of these nutrients chemical fertilizers cannot reduce deficiencies. Therefore, we must use the ability of efficient microorganisms to dissolve and mobilize soil native elements. A combination of 41.78% vermicompost, 24.35% phlogopite and 10.55% sulfur could create a proper potassium biofertilizer by providing favorable conditions for bacterial activity. Along with solubilizing activities of bacteria, the presence of sulfur reduces soil pH and thereby nutrients availability and stability increase in these soils. Because of its acidity, sulfur has a significant effect on nutrients dissolution such as phosphorus, nitrogen and potassium, and micronutrients. On the other hand, the presence of vermicompost in this fertilizer, while meeting the carbon and energy requirements of bacteria and acting as a suitable carrier, improves the physicochemical properties of the soil, increases the biodiversity of the microbial community and, as a result, promotes the soil quality and health. The evaluation of this fertilizer composition efficiency (using optimal amounts of materials) at the greenhouse and field scales is suggested.

    Keywords: Biofertilizer, Modeling, Response Surface methodology, Vermicompost
  • J. Nikbakht*, V. Eshghi, T. Barzegar, A.R. Vaezi Pages 675-688
    Introduction

    In arid and semi-arid regions such as Iran, water shortage and soil absorbable nutrients deficiency are limiting factors of plants growth. Nutrient deficiencies are compensated by chemical fertilizers. The main issue in fertilizer consumption is to use the optimal amount of fertilizer that increases water and fertilizer use efficiency. One of the newest and most effective approach for efficient use of water in agriculture is to magnetize the irrigation water. For producing magnetized water, it is crossed through a permanent magnetic field. By crossing water through a magnetic field, its physical and chemical properties improve. The aim of current research was, investigating the effect of urea fertigation by magnetized water on yield, water and fertilizer use efficiency in cucumber cv. Kish F1.

    Materials and Methods

    This study was performed as split plot experiment based on completely randomized block design with three replications from June to November 2018 on cucumber cultivate Kish F1 at the Research Farm of Agricultural Faculty, University of Zanjan, Iran. The treatments consisted nitrogen fertilizer levels at 5 levels from urea source (0%, 25%, 50%, 75% and 100% crop fertilizer requirement) and irrigation water (magnetized and no magnetized water). The treatment of 0% urea fertilizer and no magnetized water were considered as control. For crops irrigation, tape-drip irrigation system was used and for magnetizing of water, an electromagnetic field with 0.1 tesla was used. The crop water requirements were calculated by FAO-Penman-Monteith Approach on a daily basis using on-time weather parameters data of Zanjan Station. The irrigation frequency was 3 days. During the growth period, fertilization was done as fertigation approach on four times (15%, 30%, 30% and 25% of total crop urea fertilizer requirement). The first fertilization was applied 45 days after planting and the rests was carried out as 10-day periods after first fertilization.

    Results and Discussion

    The effect of urea fertilizer levels were significant at 0.1% level on yield, water use efficiency, number of fruits and leaf area, at 1% on chlorophyll index and at 5% on fertilizer use efficiency. Magnetized water was significant at 0.1% level on the all evaluated traits, except chlorophyll index. Treatment interaction effects were significant on water use efficiency, urea fertilizer use efficiency and number of fruits at 1% and no significant effect on the rest of traits. Compared with control, the highest and lowest increase in mean chlorophyll index were in 75% and 0.0% urea fertilizer level and magnetized water (21.1% and 0.4% respectively). At any urea fertilizer level, mean leaf area in magnetized water treatment was greater than no magnetized water treatment. Maximum and minimum difference between magnetized and not magnetized water treatments were in 25% and 0.0% urea fertilizer level (155.8 and 143.6 cm2, respectively). Based on treatments interaction, maximum mean of fruits number, achieved in 75% urea fertilizer level-magnetized water (32.8 number). It was 47.7% more than control. Maximum mean of cucumber yields with 50.3 t/ha, were in 75% urea fertilizer level-magnetized water that it increased 17.9, 2 and 3.8 t/ha compared with control, 100% urea fertilizer level-magnetized and no magnetized water, respectively. Results showed that application of magnetized water to irrigate plants, increased water use efficiency. Maximum water use efficiency achieved in 25% urea fertilizer level and magnetized water as much as 17.7 kg/m3. The trend of variations in mean water use efficiency showed, in no magnetized water, by reducing the application amount of urea fertilizer, averages of water use efficiency decreased but in magnetized water treatment, the trend of variations were incremental from 100% to 75% urea fertilizer level. On results, at each level of urea fertilizer treatment, using magnetized water for plant irrigating, increased mean of fertilizer use efficiency compared no magnetized water treatment. Maximum difference between means of urea fertilizer use efficiency at magnetized and no magnetized water was achieved in 25% urea fertilizer level as 74.3 Kg/Kg (367%). The results also showed, the trend of variations in mean urea fertilizer use efficiency at no magnetized water were decreasing from 100% to 25% urea fertilizer level but at magnetized water, the trend was increasing.

    Conclusion

    based on results of the current research, the optimum urea fertilizer level in Zanjan Region for cucumber is 75% urea fertilizer requirement, which by applying magnetized water to irrigate cucumber plants, mean of yield increases. In this case, in addition to save 25% of urea fertilizer amount, it is also prevented environmental problems.

    Keywords: Cucumber, Fertigation, Fertilizer use efficiency, Magnetic Water, Water use efficiency
  • Amin Mousavi, Farzin Shahabzi*, Shahin Oustan, AliAsghar Jafarzadeh Pages 689-705
    Introduction

    Soils are considered as one of the most important parameters to be achieved the sustainable agriculture at any place in the world. Additionally, the digital environment needs to have a soil continuous maps at local and regional scales. However, such information are always not available at the required scale and mapping with high accuracy. Digital soil mapping (DSM) is a key for quantifying and assessing the variation of soil properties such as organic carbon (OC) especially in un-sampled and scarcely sampled areas. Using remotely sensed indices as an important auxiliary information relevant to the study area and data mining techniques were the pathway to create digital maps. Previous studies showed that digital elevation model (DEM) and remotely sensed data are the most commonly useful ancillary data for soil organic carbon prediction. the importance of DEM and derivative data in soil spatial modelling, it was not carried out in our research because there were no sharp differences in relief, and climate for that matter, across the study area. This research aims to investigate the spatial distribution of soil organic carbon (SOC) in a study area in north-western Iran using 21 remotely sensed indices as well as two data mining techniques namely Random Forests (RF) and Cubist.

    Materials and Methods

    This study was performed on the east shore of Urmia Lake located in the east Azerbaijan province, Iran. The area extension is about 500 km2. Based on the synoptic meteorological station report, the average annual precipitation and temperature of the study area is 345.37 mm and 10.83°C, respectively. Soil moisture and temperature regimes are Xeric and Mesic, respectively. Using stratified random soil sampling method, 131 soil samples (for the depth of 0-10 cm) were collected. Soil organic carbon (SOC) were then measured. The next step was to gather a suite of auxiliary data or environmental covariates thought to be useful (and available) for predicting SOC within a DSM framework for the region studied. Then, a number of remotely sensed imagery scenes from the Landsat 8-OLI acquired were collected in July 2017. The RF and Cubist models were applied to establish a relationship between soil organic carbon and auxiliary data. Both reflectance of the individual bands and indices derived from combinations of the individual bands were used. Fourteen spectral indices relevant to four types of data including: i) vegetation and soil; ii) water; iii) landscape; and iv) geology were gathered. Three different statistics was used for evaluating the performance of model in predicting SOC, namely the coefficient of determination (R2), mean error or bias (ME) and root mean square error (RMSE).

    Results and Discussion

    The results of the descriptive statistics of determined and calculated SOC for 131 soil samples showed that the mean and median values for SOC were 2.52% and 2.11%, respectively. Also, the CVs was recorded 57.94%. Minimum and maximum recorded values for SOC were 0.83% and 5.22%, respectively. The contents of SOC was left-skewed in the data set. The RF model prediction was quite good with calibration (R2= 0.89, MSE = 0.16 and ME = 0.01). While, in the Cubist calibration data set, the Valve of RMSE and ME were increased (R2= 0.85, MSE = 0.21 and ME = 0.03). In terms of R2, The RF model showed the higher value (0.89) compared with the Cubist model (0.85) for the validation dataset. Generally, the remote sensing (RS) spectral indices can successfully predict various SOC across the study area. The covariate importance rankings showed that VARI , NDVI , CRI2 and CRI1 were the four important covariates to predict SOC in the study area. Accordingly, the changes in SOC over space were not uniform across the study area and also it means that the study area is very dynamic and evolved over time.

    Conclusion

    The results of this study showed that although variables and auxiliary data had different importance in predicting the distribution of SOC, in general it can be found by modelling the relationship between them and SOC through the model. The results revealed that the RF model was suitable for the target variable. Accordingly, the auxiliary variables had different importance in predicting the spatial distribution of SOC. Remote sensing imagery, particularly those encompassing the combined indices played an important role in the prediction of SOC. The obtained results also indicated that the Visible Atmospherically Resistant Index (VARI) and Normalized Difference Vegetation Index (NDVI) were important to predict SOC. The current study revealed that DSM using important environmental covariates can be successfully used in Iran which there is no sufficient soil databases. This research also provided a pathway to start further works in the future such as DSM relevant to the soil erosion, soil ripening, trace elements and so on.

    Keywords: Cubist, Digital soil mapping, Environmental covariates, Modelling, Random Forest
  • mohammad molaei Arpnahi, mohammadHasan Salehi*, Mostafa Karimian Egbal, Zohreh Mosleh Pages 707-720
    Introduction

    The most important factor in environmental degradation and pressure on ecological resources is rapid population growth combined with unsustainable exploitation of resources. Soil is one of the most important and worthful natural resources of environment. Land use change and deforestation decrease soil quality. Land use change also causes destruction of the evolved soils and decrease soil quality which result in permanent destruction of land fertility. Therefore, studying land use management effects on the soil quality has got an attention in recent years. Destroying the vegetation especially in the last 50 years resulted in important problems like soil erosion, land slide as well as increasing flood in the Bazoft area. In this area, degradation of the forests and their convert to other land uses like pasture, agriculture and urban or rural land use, occurs annually at high extent, in which make high damages to natural resources. In this study, the effect of land use change on soil quality indices in this area located at Chaharmahal-Va-Bakhtiari province was investigated.

    Materials and Methods

    In this research, four different managements with relatively similar conditions in terms of the influence of soil producing processes were chosen. Then, 10 composite samples from 0-30 cm depth of each land use (40 samples in total) were taken and different soil properties including soil texture, mean weight diameter of aggregates (MWD), porosity, bulk density, soil acidity, electrical conductivity and calcium carbonate equivalent were determined. One-way ANOVA was used to analyze the dataset. Tukey HSD test was applied to compare the means at the probability level of 5%. The first land use includes the natural forest with predominant cover of Iranian oak and the highest density and cover with the least human interference. Another land use is the degraded forest, caused by deforestation over the last 50 years. The third land use is the agricultural land which transformed from forest land use by deforestation in the last 50 years. The fourth land use is the walnut garden which established from agricultural land about 20 years ago.

    Results and Discussion

    The results showed that land use change from natural forest to other uses had a significant effect on most of the studied parameters. The percentage of particle size distribution was affected by different land uses, so that the percentage of clay was significantly higher in the land use of natural forest and walnut orchard than other land uses. The results also showed that the mean weight diameter of aggregates was influenced by the land use change (P <0.001). Factors like soil compaction due to livestock grazing and machinery traffic, agricultural operations and reduced biological activity increased the bulk density in all land uses compared with the forest land use. Deforestation also resulted in 6.92%, 12.05% and 14.16% porosity reduction in walnut orchard, agricultural land and deforestation, respectively. Changing management from farmland to walnut orchards also improved soil porosity by 6 percent. In the study area, the problem of changing vegetation, grazing, planting and other mismanagement increased soil pH in other land uses compared with the forest land use. The comparison of means showed that degraded forest and agriculture land uses had the highest rate of electrical conductivity which showed significant difference with natural forest land use and walnut orchard. Analysis of variance indicated that the land use had a significant effect on calcium carbonate equivalent at the probability level of 0.001. The comparisons also showed that the equivalent calcium carbonate content in agricultural land was higher than the other land uses, and there was no significant difference between walnut orchard and natural forest.

    Conclusion

    The results of the present study showed that the soil physical and chemical properties were significantly affected by land use change. Overall, it can be stated that the rate of changes in soil quality under human management and different utilization systems indicates failure in sustainable management of soil resources in the study area. Some characteristics such as soil particle size distribution percentage, soil porosity and calcium carbonate equivalent shows that there is no significant difference between walnut orchard and natural forest. However, the walnut orchards can be selected as the best management in areas where it is impossible to restore natural forests. Also, the need for stopping deforestation in Zagros ecosystem is highly recommended.

    Keywords: Land use change, soil quality, Bazoft
  • Sedigheh Salavati Nik, Saeed Saadat*, Mohsen Alameh Pages 721-735
    Introduction

    Sheshtamad area is located in the western part of Khorasan Razavi province and includes Sheshtamad city and its surrounding villages. A variety of sedimentary and igneous rock units, mainly belonging to the Cretaceous or younger age, are found in the area. A series of orogenic movements, lithofacies changes and magmatic activities led to the distribution of heavy elements that can cause environmental problems in the area. This study aimed to assess the heavy metal contamination of the soil in the extent of the study area. It has been attempted to investigate the origin of pollution and its impact on the environment using geochemical data.

    Materials and Methods

    In this study distribution and possibility of contamination from arsenic (As), lead (Pb), zinc (Zn), copper (Cu), chromium (Cr), nickel (Ni), cobalt (Co), antimony (Sb), strontium (Sr) and vanadium (V) were investigated. These variables were determined using chemical analysis of the sediments. For this purpose, network sampling was carried out at 1.5×1.5 km and 3 to 4 samples were taken from each cell. Throughout the study area (geological sheet of 1:100,000 Sheshtamad), 1248 samples of sediments were collected by Jiangxi Company and analyzed by ICP-MS method. The analysis results were summarized in ArcGIS software and elemental concentration zoning was performed by Kriging and Inverse Distance Weighting methods. Some indices have been proposed to evaluate heavy metal contamination in sediments and soils. In order to determine soil contamination with heavy metals, some parameters such as Contamination Factor and Pollution Index were calculated. Multivariate statistical analyses such as correlation analysis have been applied to identify the geochemical behaviors of different geochemical groups.

    Results and Discussion

    Surface distribution of As with values above 270 mg kg-1 was observed in the drainages of the southern part of the study area. Sr and Sb were measured with values above 2900 mg kg-1 in the drainages from south to eastern part, and above 4 mg kg-1 in south and central drainages, respectively. Surface dispersion of Zn above 210 mg kg-1 was present in the drainages from central, south, southwest and northwestern parts of the region. Cu and Pb were measured with values greater than 240 mg kg-1 in North and Northwestern parts, and greater than 110 mg kg-1 in East, Central and southwest, respectively. Surface distribution of Co element with values above 58 mg kg-1 from drainages in central, north and southwest and V with values higher than 85 mg kg-1 in central and southwest part were also observed. Finally, distribution of Cr element with values above 7400 mg kg-1 in east central and southwestern part and Ni with values higher than 890 mg kg-1 in center and north section were found.Pb had significant contamination only in a small area of the central part. Cu also showed little pollution only in a small area of the center of the region on the fringes of mining activities. According to the Pollution Index, As had a high pollution in the south and west parts. The central and southwestern parts of the study area show moderate Cr pollution, based on the Contamination Factor. Based on the correlation matrix used to determine the relationship of heavy elements with each other, some elements have a positive correlation with each other, which may indicate their common origin. For example, Co had a positive correlation with Ni and Cr indicating a common origin associated with the distribution of mafic rock units in the region. Pb and Zn have a positive correlation with each other as well as with Co and V, whereas the absence or negative correlation of As with these elements indicates a separate source for this element compared to Pb, Zn, V and Co. The presence of Cu element, despite its limited correlation with zinc, appears to be independent and likely to be more closely related to mineralization processes and mining activities in the region. Sr was negatively or very weakly correlated with most elements. It is chemically similar to calcium and can be present in carbonate sediments with gypsum in addition to substituting for plagioclases. The results of correlation coefficients with elemental zoning maps, geological maps and results of pollution coefficients showed very good agreement. The results of this study indicated that heavy metal contamination in the region was mainly due to the geological characteristics of this area. In other words, that was  mainly “lithogenic”.

    Conclusion

    The results showed that Cr in the central and southwestern parts of the region had moderate contamination and it should be considered by experts and residents of the area to prevent Cr entering the biological cycle of the region in the future. It is one of the most toxic heavy metals and contaminated areas should receive proper attention. Studies were also indicated the presence of As in the stream sediments, especially in the southern parts of the region, and it is necessary to measure the permeability of this element into groundwater and surface waters in addition to the soil. V, Sb, Zn and Co had no significant contamination and specific environmental problems at current concentrations, is unlikely. Anthropogenic contamination, except from limited mining activities, did not play a significant role in the contamination of this region.

    Keywords: Environment, Heavy Metals, Northeast of Iran, Pollution
  • S. Abdollahi*, A. Golchin, F. Shahryari Pages 737-754
    Introduction

    Contamination of soils by heavy metals is one of the most serious environmental problems that increases the risk of toxic metal entry into the food chains. When heavy metals enter the soil, they are progressively converted to the insoluble form by reactions with soil components. A variety of mechanisms such as absorption, ion exchange, co-precipitation and complexation incorporates heavy metals into soil minerals or bounds them to various soil phases. Organic acids are natural compounds that are secreted from the root of the plant and can affect the solubility and uptake of heavy metals.

    Materials and Methods

    To evaluate the effects of plant growth promoting rhizobacteria (PGPR) on organic acids production and heavy metal uptake by different cabbage varieties, a factorial pot experiment with completely randomized design and three replications was performed under the greenhouse conditions. The factors included (a) rhizosphere soils of three varieties of cabbage [Brassica oleracea var. acephala L. (Ornamental cabbage), Brassica oleracea var. italica L. (Broccoli cabbage) and Brassica oleracea var. capitata L. (Cabbage)] and (b) five species of PGPR consisting of Pseudomonas putida PTCC 1694, Bacillus megaterium PTCC 1656, Proteus vulgaris PTCC 1079, Bacillus subtilis PTCC 1715 and Azotobacter chroococcum and control (without rhizobacteria) used to inoculate the rhizosphere soils. The experiment had 18 treatments and there were 54 experimental units and three seedlings of cabbage were planted in each pot. In all treatments inoculated with rhizobacterial species, 2 ml of a bacterial suspension with 107-108 (cfu ml-1) were used to inoculate the soil of root area. The data obtained in this study were statistically analyzed by SAS software (version 9.4) and the mean comparison was performed by Duncan’s multiple range test at 1 and 5 percent probability levels.

    Results and Discussion

    The analysis of variance (ANOVA) showed that the cabbage varieties, bacterial inoculation and their interactions had significant effects (p < 0.01) on organic acids concentration, fresh and dry biomass of plant, concentrations of Pb and Cd in root and shoot of cabbage plant. The results showed that inoculation of the rhizosphere soils with PGPR species increased organic acids concentration of rhizosphere. The highest concentration of malic and citric acids in rhizosphere soil (9.59 and 118.34 mg dl-1, respectively) was obtained when the rhizosphere soils of the broccoli were inoculated with Pseudomonas putida PTCC 1694 and the highest concentration of acetic acid in rhizosphere (233.88 mg dl-1) was determined when the rhizosphere of broccoli were inoculated with Bacillus megaterium PTCC 1656. Inoculation of the rhizosphere with PGPR species also increased the fresh and dry biomass of plant, and Pb and Cd concentrations in cabbage root and shoot. The highest fresh and dry biomass of cabbage (416.77 and 76.96 g in the plot, respectively) were obtained when the rhizosphere soils of cabbage were inoculated with Bacillus megaterium PTCC 1656, the highest concentration of Pb in the root and shoot and Cd in the root of cabbage (12.20, 90.77 and 9.01 mg kg-1, respectively) were obtained when the rhizosphere soils of the ornamental cabbage were inoculated with Pseudomonas putida PTCC 1694. Inoculation of the rhizosphere soils of the ornamental cabbage, broccoli and cabbage by B. megaterium PTCC1656 caused an increase in the DOC concentration by 137, 150 and 120%, respectively, compared to uninoculated rhizosphere soils. Bacterial inoculation also increased the concentrations of available phosphorus in the rhizosphere soils and the highest concentration of phosphorus was measured in the treatments inoculated by P. putida PTCC1694. Furthermore, the concentrations of available phosphorus in the rhizosphere soils of the ornamental cabbage, broccoli and cabbage increased by 79, 71 and 111%, respectively, relative to uninoculated rhizosphere soils.

    Conclusion

    It is concluded that inoculation of Pb and Cd contaminated soils by PGPR species, especially Bacillus megaterium PTCC 1656 and Pseudomonas putida PTCC 1694, enhances the tolerance of host plants, metal uptake performance and thus phytoremediation process by increasing the metal bioavailability and biomass production of the plant. As the distribution and accumulation of heavy metals in plant tissues are important factors for evaluation of plant role in phytoremediation of polluted soils, the PGPR inoculation of rhizosphere soils can be used as a biotechnological tool to enhance biomass production and plant uptake and thus the efficiency of phytoextraction.

    Keywords: Acitic, Citric, Malic, Organic acid, Rhizobox